At face value, blow jobs can be a pretty degrading act. It's one of the many reasons they can be fun. When you're on your knees in front of someone, your eyes looking up, and his cock in your mouth, you're in a vulnerable and subversive place. With the right guy, it's a position I love to be in—I'm a firm believer in oral sex just for the sake of oral sex sometimes, and I like to give blow jobs to completion at random.
That said, no matter how pleasurable blow jobs might be for the receiver, they're just as loaded for the giver. For me? Nothing turns me on quite like a guy running his hands through my hair to get it out of my face or pulling it off my neck into his clenched hands. It's an oddly sweet and caring gesture in the middle of an otherwise dirty act, and the combination of the two is intoxicating, usually spurring me to a least double my efforts.
To men, it might mean nothing more than an uninhibited view of their spit-drenched cocks slipping in and out of someone's mouths, but you know what they say—a little goes a long way.