None. Zero. My wife has quite a few close male friends, and I feel absolutely no threat from any of them. She's a snuggler, and semi-consciously leans on anyone in the vicinity when we're all around watching a movie or something. Usually that's me, but not always.
Why should I feel threatened about this? This relationship isn't a game to be won, and they aren't my competitors.
You and your wife have a big argument. She storms out of the house, and says either:
A. "I'm going to go hang out and watch a movie alone with Dave."
B. "I'm going to go hang out and watch a movie alone with Sally."
Still, no difference?
I get that people can be open-minded and trusting, but I think there are some basic things that most people just don't do. And those things have everything to do with the underlying assumptions about the relationship between a man and a woman.
Sure, there are exceptions. But in general, there are more problems with platonic opposite sex friendships than same sex, and I think there always will be because of the scenarios I've mentioned.
Why should I feel threatened about this? This relationship isn't a game to be won, and they aren't my competitors.