Just got off the phone with a TMo BlackBerry CSR and she said there's a massive outage in SoCal and some other nearby areas, and that there was no ETA on a fix.
Edit: She said that some people have lost voice and data, others just data. And, of course, some are running fine.
Mine has been down a week today, here in Vegas!! I may be stopping at At&T this morning I have a contract and it states they may not be able to provide service ALL OF THE TIME! What a safety net!