again, we've only seen Black Widow
>as an assassin who uses sex as a ploy to get what she wants
>out of people (including the "flirting" with Cap mentioned
>above) in the past and suddenly she's tending bar (?!?!) and
>trading forced, cheesy romantic comedy lines with a nerdy
>scientist.

people change. similar to how stark is trying to get out of the superhero game, she's looking for a sense of balance. no one is 100% stone cold killer, you simply can't be. actually, it all makes sense after cap 2, cause she was flirting with cap but in a way that teased her wanting a relationship. the key line in all of this was the one about how all her friends are fighters so she became attracted to the one who's trying not to fight. while i've admitted that her level of flirtation was a little too overt in that scene, how people didn't understand the relationship after that line is beyond me.