I don't know how people masturbate to celebrities. Sure I've had my crushes but they're all on dead celebs. As far as fantasizing and cumming to the thought of engaging in a certain act with someone it would most definitely (and always is) over someone I know.
Lately it's been Katy Perry for me......and on extra dirty days it's Miley Cyrus. Terrible. I know, but she has me cumming hard in seconds.
The only thing I can think of that would be more absurd than jacking off to a celebrity, would be jacking off to the bra ads in a Sears catalog, which sadly, I did at 14 years old. Come on, the woman had some amazing tits.