Duncan writes to warn us of a Windows Phone 7 feature which may turn out to be a bug for users with limited data plans, such as AT&Tâ€™s 200 MB cap.
Windows Phone 7 protects users with limited plans by only allowing downloads of more than 20 MB from Marketplace over WIFI. It turns out however that if this WIFI connection is dropped the OS will happily switch over to 3G to complete the download, which is somewhat of a feature really, but of course can easily suck down a significant proportion of your data allowance.
The lesson is therefore to make sure you have stable connection when downloading when out and about if you have a small cap.
Thanks Duncan for the tip.