I think it's hard to decide how to handle this. T-Mobile has a breach, you get upset and move to O2, Verizon, ATT, etc. The thing is, those companies might be worse at security. We don't have any good way of judging this, and like Thom notes, everyone will get breached at some point. Security just isn't mature enough, and humans are a big problem still.

I'd like to think  I would  stop and think about the issue, what happened, how the company handled things, and then decide what to do.