As Dave Winer mentions we should be worried about things we take for granted on the web. Like GitHub.
I only use it to share some code snippets and a few WordPress plugins (so any change in how it operates wouldn't really affect me) but I know there is so much stored there that could really suffer if an acquirer decided they wanted to shake things up in the name of profit.
I'm not entirely sure how I feel about a possible purchase by Microsoft. It's certainly not the company it once was but having something so core owned by one of the big four makes me nervous.