Interesting. One concern I'd have is that I actually find the segmentation of data / sms / voice to be a feature because it corresponds well to my priorities. For example, I can turn off auto-sync to save battery power or to decrease distractions from my phone, but still have SMS and be available. If people really want to get a hold of me asap (and they're important enough to me to have my cell number) they will text me.

Of course there are alternate ways to allow users to do this--Google circles and Facebook lists come to mind--but they all are a pain to maintain, use.