I don't think it's embarassing. This happened to me today. I was walking down the street and passed a man that smelled great and it was a type of scent I might be interested in.
I just tapped him on the shoulder and said "Pardon me, I hate to bother you but I was wondering what cologne you're wearing. It reminds me of something and I was curious." He wasn't offended, but he didn't know either - he said it was something he just grabbed.
Now, if you go up to a guy, stare him in the eye and say something like "Hi, handsome. You smell divine! What is that delicious smell?" You might get a different reaction.