Out of curiosity, have you watched the gameplay videos? If you have, was there something specific in the videos that reminded you of Borderlands? You're not alone, I've seen others draw the comparison too.
Like Badman, I'm a big fan of Borderlands (I still need to play the latest DLC and finally reach level 50), but I've never really seen the comparison.
I loved Borderlands, but it didn't last long for me. I got 3 of the 4 characters to level 50 and I wasn't ging to play as Brick anyways.
I also don't see the similarities between them. Borderlands was a little cartoony and Brink is crisper. I do see they both are shooters/rpg like (with exp and upgrade to character), and they both have "B"s in their names, but that is it