You could speed this up even more by using a smarter searching method than memcmp. Something like http://en.wikipedia.org/wiki/Knuth–Morris–Pratt... should be much better than just moving ahead one character at a time, though depending on the size of the two files, memcmp might be faster just because of the (much) faster SIMD instructions, instead of the algorithmic improvements from KMP.
Facebook themselves mentioned they were #1 in Canada at the Toronto Facebook Developer Garage. Hopefully they are looking at Comscore and not Alexa for that date, but either way, it does seem surprising.
To get from 18 to 30, you have to consider Facebook has other income streams than just display ads.
- Sponsored groups - Facebook has been known to ask in the range of $100,000k/month for these, but I don't believe they sold many. - News feed ads. No idea what they charge for this, but this has to be a premium on their CPM for ads. - Gifts - though this is likely declining with the introduction of F8 and Free Gifts.