So the main issue in the case of B2 (which is region-free) is figuring out how trustworthy the vendors are. I just read the fine print on CDKeyDeals and it says that they actually send you a photo of the retail box, so I guess that’s cool. Too bad they’re sold out now.
Edit: This one seem trustworthy to you? http://cdkeyshere.com/borderlands-2-cd-key.html?tracking=4e4656fceacc7