We just noticed that Peter Rojas of GDGT had some issues installing a non-Market application with his Motorola Atrix 4G. We’ve just confirmed that sideloading of apps is not supported with the Atrix 4G. While it’s likely there will be alternatives to accomplish this, it’s a bit disappointing to see this not supported out of the box.

Really? I find it funny people think AT&T wouldn’t lock the atrix up
I’m sure at&t will load it up with there BLOaT Ware Grrrr just thinking about it makes me want to switch carriers
ive been sidloading like crazy with droid explorer. There is very little bloatware and what there is can be easily deleted with the native app manager. you can wireless teather. the list goes on.
super one click will solve your problem