As far as I know, in comic canon Black Widow started out as a baddie who seduced Hawkeye so she could use him against Iron Man. Things went off and on from there, but I'm pretty sure they haven't been together in the comics for a while. Marvel movieverse seems to take some elements from the comics and then go its own direction. I think their movie relationship is a different beast to the comics. They do have a similar relationship in the Avengers: Earth's Mightiest Heroes cartoon.

As long as the pimping relates to Clint/Natasha, it's not only allowed, it's encouraged!