It's always a balance - do you want something you have complete control over, including the possibility to break it, or you want limited control but be sure that even if it breaks, you get a new one? The platform itself is "open enough", but manufacturers and carriers are making a business out of it.
And for the record, I think you can click "clear data", and also use some process monitor to kill your unwanted apps. My facebook app doesn't have these issues