*shrugs*
In regular continuity they have to rely on each other sometimes, (I think that scene where Eddie crashes at Pete's place on the counch in Max Carnage was funny) but doing this has been described as like having to go in for a root canal.
In the Ultimate Universe they start out as friends. It's almost like a sibling relationship. With Pete breaking into the lab and "borrowing" Eddie's experiment. And when Pete tries to warn him about it, he's giving Eddie, who is older, orders and it's an affront to his pride. It's like your little brother giving you an order what to do. Of course you do the opposite-- even if you know the result will be bad just to prove that "you're not the boss of me".
Oh and in the last panel w/ Pete looking for Eddie you can see some clawed feet in the corner-- Eddie has been following and watching Pete as Pete goes looking for Eddie, and Pete realizes that he is the only one who cares that Eddie is gone.
I'd like to see them play up that angle when Ultimate Venom returns in a story arc or two. That and his reaction to Gwen's death. He was obviously attracted to her.
http://www.geocities.com/sean_ropp/Venom_DD.html
There is the proof.It says he's about 27-29 years old.