Does SwiftKey phone home what users are typing? $250 million seems a lot for an input method, more reasonable for a large set of data for them to analyze.
Actually, it does way more than that.
It syncs between your different devices. And you give it access to your gmail (if you want) so it can mine data you inputed years ago, which is weird they didn't mention the gmail part. I have far more data on my gmail account than anything on Twitter, SMS, or Facebook.
Personally, I sync my gmail with it, plus everything else, but I don't mind. That app is super intrusive, yes, but it's also why it is so good. It knows what I am going to type before I type it and it's the only app I know that allows you to mix different languages when writing.
It kind of sucks that Microsoft bought it. Google is the really one that should have bought it instead.