I used to think this as well, but there's a problem. What if FB ads are not as good a monetization solution for publishers as Google ads? This seems quite poss

I used to think this as well, but there's a problem. What if FB ads are not as good a monetization solution for publishers as Google ads? This seems quite possible. Facebook advertising is much much cheaper than Google advertising on a per-click and per-impression basis. With Google ads, advertisers are used to paying as much as $20/click in some areas. I've never heard of a FB advertiser paying more than $2/click. Likewise, CPMs on FB are in the single digit pennies quite often. On the web, banner ads are around $0.75 CPMs for decent sites. Facebook might have looked at this and might believe that if they launched a network like this, the payouts just wouldn't be able to compete with what Google's able to give publishers.