Yeah, theres the obvious condensation problem. Though if the fridge was sealed that shouldnt matter.
The other problems are that you'll be lucky to find any cheap fridges that will deal with the heat output from a Phenom II X4 and the rest of the system, and even if the frdge can deal with the heat, its likely to kill the compressor pretty quickly (due to running hard full time).
If you were runnuing a sealed fridge, the power costs compared to just the computer would be over double (if the fridge isnt removing as much heat as the complete computer outputs, the temps will just rise). If its a unsealed fridge, you're back at the condenstaion problem.....
It sounds like a good idea, and some people have done it. But if it worked as well as people think it should/could, overclockers would have used it as a standard method.
The overclockers who did play with the idea of fridges mostly moved to 'phase change cooling' using air conditioner or fridge compressors.