The excessive data usage that Windows Phone 7 users have noticed is an issue that Microsoft has admitted, but so far, it has refrained from naming which third-party app is responsible. That is, until an investigation showed that Yahoo Mail is the culprit, forcing both companies to finally acknowledge the culprit.
Ars Technica - Microsoft and Yahoo have finally acknowledged that Yahoo is, as has long been suspected, culpable for Windows Phone 7's excessive data usage. Microsoft admitted to a problem a couple of weeks ago, faulting an a third-party service but infuriatingly refusing to specify which third party.
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