How Facebook Is Killing Your Data Plan
A couple weeks ago, I got a warning from AT&T that I had used almost half of my monthly data allowance. I couldn't figure out why that would be. I hadn't been away from wifi any more often than normal. I wasn't streaming video across my mobile. It didn't make sense.
Then a friend shared this status, and it WAS what had happened on my phone. I recommend making the suggested change. It made a big difference in my data usage.