I read a couple of reports from Engadget and the BBC that some Windows Phone 7 devices seem to be consuming data at an extraordinary rate. I have been using Windows Phone 7 devices since last July and find this reported anomaly hasn't affected me with the HTC HD7 or Samsung test WP7 device.
I went and checked my T-Mobile account for data usage for the past several months. Even with my switching between a couple of devices (mainly the Nokia N8) for a few weeks here and there, the maximum amount of data I have consumed has only been 1.6 GB in a month. This is a very reasonable number considering that I use my phones a LOT during my daily two hour train commute and throughout the day, including downloading full songs and albums via the Zune Marketplace. My HTC HD7 was purchased on launch day on 8 November and I keep the WiFi radio on all the time so I can connect automatically to WiFi at home and 3G everywhere else.
The BBC reports that Microsoft is looking into these reports, but based on my long term experiences it appears that it is not a Windows Phone 7 issue and may be related to specific handsets and carriers. I think it is likely to be an application that is either preloaded by a manufacturer or carrier or else something that is commonly used by the people seeing this pattern. I have a TON of 3rd party applications loaded on my HD7. I even have an Exchange account and 2 other Gmail accounts connected through Exchange that are all setup for push email so I should be consuming the maximum amount of data possible as well.
BTW, I also have the send feedback setting enabled, including the ability to send this feedback via cellular data connection. The Find My Phone feature is also enabled, so again, I have the maximum data settings enabled on my HD7 and am NOT seeing extraordinary data consumption. I enabled the feedback to help Microsoft, but if you are concerned about battery life and data you should probably disable this setting.
I am not the only one seeing normal data usage as you can see on the Windows Phone Secrets website of fellow Wiley WP7 book publisher, Paul Thurott. As you can see Paul uses much less data than I do and while his chart shows he is using more than his previous iPhone on AT&T he was using his WP7 device heavily as he wrote his book.