a) Probably, though I bet I don't know most of them. If I were MS M&A I would bet disproportionately on mobile, though, because that's an area they need to nail if they want to stay relevant. If they could get 70 out of 200, that'd be a darn good start.
b) Individually, not terribly likely. Collectively? Sure. (And it's $35M each, but the exact number isn't the point - let's say you could offer every ycombinator and techstars startup an average of $35M each, you'd likely end up getting two or three Dropbox-esque gamechangers, a few dozen decent products, and 150 otherwise good ideas folded into MS and dead-ended.)
To the extent that my math was way wrong, I think your point carries more weight (meaning: you're an order of magnitude better than I thought). I'd say if they bought the top 10 mobile plays for $70 million each they'd have a much better expectation (assuming that the acquisitions could be digested--risk which itself carries a significant reduction in expected value).
b) Individually, not terribly likely. Collectively? Sure. (And it's $35M each, but the exact number isn't the point - let's say you could offer every ycombinator and techstars startup an average of $35M each, you'd likely end up getting two or three Dropbox-esque gamechangers, a few dozen decent products, and 150 otherwise good ideas folded into MS and dead-ended.)