Inevitably the people who are looking to jump ship from Infosys or other low-end consultancy are woefully underqualified for even entry-level positions. I've actually interviewed people from these shops who cannot write Hello World in a language of their own choosing, I've also had people who didn't know what a tree data structure was. I'm unsure how Infosys et al can farm these guys out for such high hourly rates, it's surely criminal.
Sniping from Infosys and Wipro isn't worth it for top companies because there's hardly anyone there worth sniping. They do try sometimes though, since inevitably there is a diamond in there just waiting to get the hell out of dodge. There is effectively zero intersection between the types of developers Google wants, and the types of developers Infosys wants.
As for who Google/Microsoft/etc are trying to hire... I wouldn't call it "top talent" exactly. The H-1B pool in these companies isn't a parade of who's whos of the software industry, though some of them are certainly top-1% coders. It's more like "very good coders" - people who know the tech, learn fast, have solid fundamentals, and get shit done - which is more than can be said for the majority of the talent pool. Simply eyeballing it, I'd say that Facebook/Google/etc are targeting the top 5-10 percentile of coders.