Heh, you'd rather be PKed once in a while when trying to do trades, than not be able to get into the trade centre at all, trust me. If the trade centre's made PK-free, they will just hang around outside it and stop anyone from getting in...or move to another place (i believe the pub was a past location?) and clog that up and stop it from being used properly and safely.
O, btw, you'll probably have people saying "O if u dont wna b pked, dnt go in Bmode, nuuuub :P" at some point in this thread
