It depends on the guy and gal-- women fake it sometimes to make their man feel better about the act, when sometimes in the womens eyes its about as exciting as watching the evening news. A man needs to know that a women takes longer to reach orgasm then a man does and women need to have some kind of foreplay to signal to her body that it's time. Women can't go from 0 to 60 in sixty seconds like a man. We need a little more time. An experianced man will know this therefore eliminating the womens need to fake it.  All in all alot of women fake it because they don't want to disappoint their man into thinking he ain't no good, it's our little way to boost ya'lls ego. My experiance though has taught me to be honest and tell my man that I need a little down south time to get my motors running- then it's full throttle from there.....