I have given head to one straight man since I like to give it wasn't much of a big deal to me at the time. I'm 18 and just entering college, and what I'm about to tell you happened the week before classes started. I am bisexual myself but lean towards the gay side (about a 4 on the Kinsey scale).
There are those that would give head or something along those lines without ever wanting reciprocation, something which many straight men would die for in a woman. Straight guys usually don't think of the immense resources available to them in the homosexual and bisexual community.