Well I see that I am not the only one that got a surprise in that my data usage was reaching the 75Mb area by the end of my first week with this phone and doing so without my knowledge. So far, I have found that the first culprit was the really cool default HTC clock which also includes the local weather wherever you might be. The weather updates uses your "Mobile Network" or data plan to do it's deed. The other things are that quite a few apps use your data plane for either setting up the app or updating
the app. The best way I have found so far to avoid this is of course using wifi whenever you can but if that is not always an option such as when you are truly mobile or in a non-wifi environment, you can do these steps to help shut down your data usage... First, select "menu", then select "Settings", then select "Wireless and networks", then at the bottom of the screen is the "Mobile network" selection. Make sure it is not checked. It does not hurt to keep tabs on this setting to make sure that some app or widget has not changed this setting inadvertently. Now while you have the Wireless& networks screen open, look at the next category down which is "Mobile network(s). Select it and make sure that none of the boxes in this category are checked. This should
conclude making your phone secure from unexpected data usage without your knowledge. There is one app that I just found out about that you might want to look at and probably want to install and use and that one is called "3G Watchdog". If you want more info on it, that can be accessed here... http://www.cyrket.com/p/android/net.rgruet.android.g3watchdog/
. It seems that is will be beneficial in that it uses icons on the home screen which tell you at a glance what is happening with your data usage. I hope this helps but I also would like to hear about any other suggestions on this subject.