Google probably can't become a startup again, but it can probably start some kind of internal startup-like culture to spur internal innovation. If it "funds" groups of employees to essentially build an autonomously run startup (and rewards successes with $$$) it can probably save tons of money over the current acquisition strategy it has (many of which aren't really turning out to be great performers for Google).

With YC level success rates, it could be a great strategy for them.