I know I heard about the whole unlocked SEs can be activated on any network, but how does that work? And would they be compatible with Verizon Wireless?
no - verizon operates on CDMA [basically an internal sim card that you cannot remove] and most if not all sony ericsson phones operate on GSM [removable sim card]
however, if you do find an SE that can operate on teh CDMA network, you don't have to unlock it - you just have to do some stuff through the computer [changing the internal sim number from the old phone to the new phone - done online for free, i know because my friend did this] and you're set.