I swear if brink is another Borderlands as far as hacking/modding goes I swear I am going to be so disappointed.
I think the real issue with modding in Borderlands was the fact that you could trade. The whole trading market kinda falls apart when people can make any item they want to trade with.
With brink, I wont be surprised to see players that unlock everything with mods, but it doesn't really affect the rest of the player base. If you're in a game with a modded host, just leave.
Players with modded items don't really matter much either. All of the weapons and attachments can be unlocked in 8 challenges, half of which are basically a tutorial. All of the clothing can be unlocked by reaching level 20, which can be done in a day if you're working at it. So they aren't cheating to get anything that has prestige.
The only real possible losses that I see from mods are leaderboards, since I don't know how that's set-up. Might have people sending in level 3 challenge times of one second or something.