Multiplayer will be capped at level 5 without the code on the back of the manual. Obviously if you're buying from Steam you won't be affected since you can't trade it anyway.

As I actually plunked down for the pre-order this royally pisses me off (this is the perfect kind of game for swapping with buddies or selling off once you get tired of it).

It's called the Elite Pass for anyone wondering.

Link: http://www.spacemarine.com/forums/topic/3376

That's just BS. But, TBH, it doesn't majorly bother me, having played the the demo and pre-ordered, being some sort of WH40K fan.
Space Marine is indeed one of those games that are great for borrowing. Did this all the time with friends and cousins when I was younger. Good times.
Sure, you can play the SP all you want, but it's bit stupid if one of your buddies is MPing gamer.