"Today at the TechEd North America 2010 event Microsoft has confirmed Windows Phone 7 developers will be able to register a number of devices which unlocks the capability to side-load applications on to devices directly from development tools such Visual Studio or Expression Blend. Initially, Microsoft will offer three device registrations per Marketplace account ($99 per year) tied a Windows Live ID. Developers who legitimately require more will be considered by Microsoft on a case-by-case basis."
The rumors we were hearing last week are true - Developers will be able to unlock devices without having to buy special "unlockable" devices. Pretty cool - All you need is a phone, a $99 per year developer account, a mess of free tools, and a dream to start building!