Official: No Sidleoading Out of the Box
Motorola Atrix 4G Does Not Support Non-Market App Installations
Motorola Atrix 4G Does Not Support Non-Market App Installations

You say cripple.
Some say security.
How about AT&T is afraid of casual users installing tethering apps on their own or apps that AT&T forces you to pay a subscription while every other carrier offers it for free (like Where)? I think it's telling that the Android Market is missing quite a few apps on AT&T, yet other carriers allow the full thing...I think theres two sides to this coin,
Heads: at&t doesn't want customers to be able to do everything to their phone to keep a little control or
Tails: SJ has been whispering a little Apple policy into at&t's ear over the last few years and at&t has been listening when they shouldn't have been.
I'm just bs'ing really, I have no idea why at&t does what they do sometimes
How about AT&T is afraid of casual users installing tethering apps on their own or apps that AT&T forces you to pay a subscription while every other carrier offers it for free (like Where)? I think it's telling that the Android Market is missing quite a few apps on AT&T, yet other carriers allow the full thing...
You could also go to the new online web market @ https://market.android.com/
B) 1) Put phone in airplane mode
2) Reactivate wifi
3) Head on over to the market and get Where, PdaNet, etc
Where is useful for me to finding cheap gas prices and movie schedules. I downloaded the free version off the market though. Screw AT&T and their attempts to nickle and dime me over apps that already freely available.Where is typically preinstalled on at&t phones and if you use it read the fine print it is a 2.99/mo subscription and shows up on your bill under subs and other charges as 2.99 find people/places. More bloatware IMO
Where is useful for me to finding cheap gas prices and movie schedules. I downloaded the free version off the market though. Screw AT&T and their attempts to nickle and dime me over apps that already freely available.