What did Microsoft get when it signed a deal in August to serve ads against search results on Facebook? The right to make money off the second-fastest growing search engine on the Internet, according to a ComScore study. Facebook served 173 million search queries in July 2008, up 10 percent from 157 million in July 2007. Facebook doesn't allow its users to search the rest of Web from its site. Even then, its search engine reached a sixth the size of Microsoft's own.A dandy of a deal for Microsoft? Perhaps not. Look closer at ComScore's chart and you'll see that the fastest-growing search engine is MySpace, which gets all of its search ads from Google. Google doesn't make much money from them, though, CEO Eric Schmidt admitted earlier this summer. Probably because no one searches MySpace for something to buy. Will Facebook prove any different?