In 24 hours, I've gone from 2.8GB to 3.44GB downloaded by Exchange Services.
Just got off the phone with customer service. They suggested that I clear the application cache. I was surprised that he didn't know what Exchange Services was - I had to tell him. To clear the cache, go to Settings > Apps > click All at the top of screen > Exchange Services and clear both Data and Cache. For good measure, I also deleted the hotmail account I was using with Exchange Services and booted into safe mode and back again. If it continues to download data, I'll disable it.
I'm on the latest OS release, v4.2.2.
This is costing me bandwidth and throttling. I'd be VERY pissed if I were paying by data use.