When they first opened up the search page it was refreshingly naive about data security. My numbers may have been skewed downwards because not all profiles wer

When they first opened up the search page it was refreshingly naive about data security. My numbers may have been skewed downwards because not all profiles were indexed. But I cross-referenced Uni + Year searches with full dumps from Uni tabs and it matched up pretty well (ie, UPenn has X class of 2009 students in real life, search turns up 0.53 X, UPenn dump turns up 0.58 X). Then again, not all users may have institutional affiliations. But around the same time FB launched ad targeting (http://www.facebook.com/ads/create/ http://www.facebook.com/ads/create/) which tells you how many people they can reach. When set to no filtering it returned 19.2 Million. edit (removed QED): I just double-checked that page today. They are claiming 62M in US, 18M in UK, 11M in Canada, 8M in France, 2M in India, 2M in Hong Kong, 2M in Germany, etc. It's possible those numbers add up to 200M, but it's not clear whether they have changed their definition of user for the purposes of this app.