The Windows Phone 7 device hacks are slowly trickling out regardless of the security measures. A hack released last week allows for direct file transfer to your device via USB, and now a hack has been outed that lets even non developers bypass the Marketplace and "sideload" any app you desire onto a WP7 device.
The new tool is called Chevron WP7, which is compatible with Windows XP SP2 and up, and unlocks your phone so that you can install apps without going through the Windows Marketplace. For now, Microsoft only allows this function for those with developer access and wouldn't dream of rolling it out to the general public due to Microsoft not being able to look over or approve sketchy apps. Check out the step by step process at the Source Link.