Mojtaba Torkjazi†, Reza Rejaie†, Walter Willinger‡

† University of Oregon‡ AT&T Labs-Research

WOSN’09 Barcelona, Spain

MotivationA majority of empirical studies of Online Social

Networks (OSNs) has focused on their associated friendship graphsWhat about the temporal dynamics of OSNs?What about the “active” portion of an OSN?

A majority of empirical studies of OSNs has examined the growth of these systems What about the patterns of decline in user

population?What about changes over time in user activity?

A majority of empirical studies of OSNs has been based on connectivity informationWhat about timing information?How to obtain relevant timing information?

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Related WorkCharacterization of popular OSNs via their friendship graphs

OSN characterization in terms of well-known graph metrics[Mislove et al.’07, Ahn et al.’07, …]

Examining the evolution of friendship graphs of popular OSNs OSN evolution in terms of growth metrics and models[Kumar et al.’06, Leskovec et al,’06, Leskovec et al.’08, …]

Beyond friendship graphs: Activity graphsStatic case (Cyworld) [Chun et al.’08]It’s all about dynamics! [Willinger et al.09]User interactions in Facebook [Viswanath et al.’09 –

WOSN’09]User interactions in Flickr [Valafar et al.’09 – WOSN’09]

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This StudyWe examine the evolution of user population and user

activity in MySpaceUser arrival/activity/departure, life cycle of MySpace

Why MySpace?It is one of the largest and most popular OSNsIt provides several features making our study

feasibleMain challenges

OSNs are often studied when they are popular and the number of departure is negligible

Popular OSNs tend to hide the information about user departures

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MySpace Features (I)Provides explicit profile status

PublicPrivateInvalid

Availability of users’ last loginEnables assessment of the level of activity among

usersImportantly, allows inference of population growth

of MySpace (see later for details)Global visibility

http://www.myspace.com/user_id

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MySpace Features (II)Monotonic assignment of numeric

IDSearched periodically for currently

smallest unassigned ID and checked that all larger IDs are unassigned; after waiting for a short period, we observed that the smallest unassigned ID (and others after it) are now assigned.

Found no apparent patterns in gaps between consecutive invalid IDs

No evidence for re-assignement of deleted IDs

Makes the selection of random samples of MySpace users easy.8/17/2009 WOSN 2009 - Barcelona 6

No visible pattern

MeasurementFeb. 26th 2009: MySpace ID space [1 …

455,881,700]50 parallel samplers to collect 360K users in less

than 12 hours (0.1% of MySpace population) Using HTML parser to post-process the

downloaded profiles and extractUser s’ profile status (invalid, public, private)Users’ last login dateUsers’ friend list (only for public profiles)

Unable to parse last login info for 0.96% of public and 0.08% of private profilesLast login info is not provided or is provided with

obvious errors (e.g. 1/1/0001)

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On the Population size of MySpace

Population of valid MySpace users (Feb. 26, 2009) was about (41.5 + 17.3)% of 455,881,700 = 268M

Compare with www.myspace.com/tom who has 266,029,430 friends (Aug. 13, 2009)

How has MySpace grown during the past years?How many “active” users are there in MySpace?

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Total Invalid Public Private

362K 149K (41.2%) 150K (41.5%) 63K (17.3%)

On User Arrival

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Public users

What does user ID say about account creation time?

Plot user ID vs. last login of that user for all our users Private

users

On User Arrival

32% of public and 18% of private users are touristsDiscovery of “tourists” enables accurate estimation of user

account creation time based on their associated user ID

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Tourists

What does user ID say about account creation time?

“Clean edge”=

users whose last login

is shortly after their account creation

time=

“MySpace tourists”

On MySpace’s Growth

Use the observed uniform spread of tourists across entire ID space

Estimate account creation time by last login time

Estimate account creation time of all sampled accounts based on their ID.

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April 2008

Estimating the user population of MySpace in the past?

Slope of the top line shows the growth rate of MySpace population Exponential growth until about April 2008 Visible knee around April 2008 followed by a slow-down in growth

On User Activity (I)

“Active” = login into MySpace within the last 10 days

More than half of public users haven't logged into MySpace in the last 100 days

Less than one third of private users have logged into MySpace in the last 10 days

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How many active users are there in MySpace?

MySpace has about (15% * 41.4% + 35% * 17.3%) * 445,881,700 = 55M active users.

On User Activity (II)

More active public users in the first half of the ID spaceMore inactive private users in the first half of ID spaceMore med active private & public users in 2nd half of ID space

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Public users

Age of a user in the system vs. level of activity?Private users

On User Activity (III)

No strong correlations in generalExcept for the very inactive users who tend to have

very inactive friends8/17/2009 WOSN 2009 - Barcelona 14

Activity of a user vs. activity of the user’s friends?

Public users

On User Departure

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More public and private profiles in the first half of ID space

More invalid profiles in the second half of ID space

Users joining the system earlier have been more likely to keep their accounts than newer users

Are newer users more likely to leave than older ones?

MySpace Life Cycle (I)

Slow-down in the growth rate of MySpace is related to emergence of Facebook

Informal evidence (Alexa.com): Daily accesses to Facebook surpassed that of MySpace, at around April 2008

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Possible reasons behind MySpace’s decline?

MySpace Life Cycle (II)Scalability

System design can’t cope with exponential growth rates? How to effectively link millions of like-minded users?

Security The larger the more attractive to hackers and

spammers? More privacy violations and unwanted traffic?

Innovation In the absence of constant innovation, initial excitement

of users fades away?

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Possible causes for users migrating from one OSN to another?

Is it the case that OSNs become the victim of their own popularity and success?

ConclusionsWe examine the evolution of user population and user

activity in MySpace and we found thatEstimated population of MySpace users with valid

accounts is about 268M, of which only about 55M are active users (as of February 26, 2009).

32% of valid public and 18% of valid private profiles belong to tourists = users with last login shortly after account creation

We exploit the existence of these tourists to estimate the population growth of MySpace since it’s beginning

We observe an exponential initial growth rate for MySpace followed by sudden slow-down around April 2008.

We speculate about possible reasons for why some OSNs are able to compete and strive in the Internet's OSN eco-system, while others decline and die out.

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Future WorkWhat about other OSNs?

Twitter, Flickr, YouTube vs. FacebookMeasurement challenges

Obtaining more/any timing information for user activity

Tracking migrating OSN usersWhat factors are key for the success /failure

of OSNsTechnological, socio-economical, …

Thank You

Questions?

Websitehttp://mirage.cs.uoregon.edu/OSN

Contact for code and data:Mojtaba Torkjazi

moji@cs.oregon.edu