Thor movie question (Spoilers!)?

So for those of you who saw Thor you know that Hawkeye makes a cameo. The only problem I see is he wasn't an original member of The Avengers was he? How are they gonna explain him joining so early in The Avengers movie? If I remember right I think he was part of the second team, not the one with Iron Man, Hulk, Captain America, Thor, Wasp and Ant Man. Surely comic book fans are gonna notice this continuity problem and complain as always.