Congrats to Instagram! Can't say I am not bit disappointed though with all the startups getting gobbled up by much larger companies. What's next? Pinterest?
Not saying I'd like to see it happen, but Pintrest would fit in well with Google+, moreso than Facebook. Google+ really does the sharing+comments thing well.
It's hard to know where to root. Independent start-ups give great competition to the big players, but I know a lot of people go into an MVP with the goal of making a large exit. It's a great way to get funding for your next startup.
Why are you surprised? Most startups are built to either go IPO or exit through a buy out. Considering many startups (including Instagram) do not even come up with a profitable business model, it excludes IPO and therefore only leaves an exit as a way for investors to recoup their investment.