The negative: - added friction to building a startup, since one exit path is harder.
The positive: - more focus on profitable companies, as opposed to ones that will only be viable if acquired. - a more competitive market, which might be better in the long run for start-ups
I don't think the question we should be asking, though, if the effect on startup culture. I think what we should be asking is: what is the effect on users/consumers?
To that end, imagine if the online ecosystem today included Instagram, WhatsApp, DoubleClick, Zappos, YouTube, Waze, just to name a few. Yes maybe some of them wouldn't have survived, but maybe that would have been the right thing to do.
And I think that's the question regulators should be asking too. Whenever a large company is acquiring a smaller one: is this clearly good for consumers or not? I mean, if Intuit can make a good, believable case that this is good for users (ie "Once we buy Credit Karma we can give all our users free tax filing) or something like that, by all means, that's great... but I doubt that's what's happening here.