Thanks for your comments. I’m sure it would be hard to estimate real life friends, and since our analysis depends on a real life estimate, this could through everything into question. In our follow-up work, we have been asking users to list the number of contacts they have in their email address book. Perhaps this is a more reliable indicator than an estimate—either way, this would be a hard number to gauge accurately.

I think we first thought to look at mean network size since it was an easy number to calculate. If it’s the wrong metric to be using to study power law distributions, is it better to just visually plot the distributions for a comparison? Or is another metric better?

It is still kind of interesting that mean real life network size was about 150 for both Facebook and Twitter users.

I agree that the conclusion that FB is closer to real life isn’t very surprising. There could be tradeoffs to using a FB vs. Twitter network for social search support. While you may trust your friends on FB more (presuming they are also “real life” friends), there may be greater diversity among a set of Twitter followers. Trustworthy friends could provide good advice/opinions, but a diverse audience may provide a wider array of non-overlapping information that may help you see the scope and breadth of a problem space.

(1) it seems that the estimates that people make about the number of real life friends would have to be wildly inaccurate. Don’t you think so?

(2) In the figure for “mean network size”, isn’t the metric weird? You used mean (or averages), when we know that the underlying distribution has to be a power law, so that means the ‘averages’ do not represent much about the actual distribution. it’s good that you used a non-parametric test later.

(3) the conclusion that FB is closer to real life is perhaps not surprising, since that is the one where people are expected to use their real name. On twitter, users don’t have to use their real name, and some people have several accounts. People actually follow fake accounts or organization accounts.

[...] brynnafred – Just how virtual are virtual social networks? "Our data appeared to be highly non-normal. Users’ online social network sizes varied greatly from 5 to 1495 (Facebook average: 314; Twitter average: 126). Real life estimates also varied from no friends to 1000 friends (Facebook average: 168; Twitter average: 143). (See below.) (Side note: It’s interesting that real life network sizes averaged out to be very nearly Dunbar’s number of 150: or the limit of the number of active social connections that humans can maintain." (tags: socialnetworking facebook twitter) [...]