My Dodgy Android App experience
I have to admit, I have encountered a dodgy Android app.
I installed the official Microsoft Hotmail Android app earlier in the year, and it worked fine for a while. Suddenly one weekend, it developed a fault and slurped my entire data quota (500Mb) in under 2 days. It was actually using over 300Mb a day in data until I identified the culprit and uninstalled it.