i think it's entirely proper to hold some things back. it's the negotiation protocol.
for example, don't bring up something like a fetish unless you've reached a level of comfort between the two of you that you choose to share such a thing.
take a fictitious example. if my current boyfriend bleated out that he loved to suck and worship feet as soon as we had met and spent the next 5 minutes expressing his desire to lavish my feet with tongue baths, i would probably have stood up and walked out before the waiter had even inquired about drinks.
but if he were to bring it up now, i'd have no problems with it.
sort of like guys that have their anus spread wide open for you as their default picture. sure in the end that's where my penis is going and it's going to be quite pleasurable, but that isn't the photo you introduce to your mother... :-?
there's a time and place for every component of a relationship. the adept person figures out what and when to bring up something to a prospective boyfriend :)