Well, I know from very recent experience when you have friends living together and a girl that one of you knows gets with the other guy...mmmm things could get ugly so he's just covering all his bases.

But you can tell, just by reading in this forum how men act when they're head over heals for a girl. If that enthusism isn't present, then it's just a little thing, maybe some pillow talk.

Keep your options open.