Actually Gandalf, you are closer to being right then some of the other responses in this thread. Age of consent varies from state to state and it isn't always 18. Many states the age of consent is 16 and lower and there are some states that have laws to make exceptions for say a 19 year old dating and having sex with a 17 year old for example or even if they are both under 18 or if the age difference is close. That too varies from state to state and some states even allow for other exceptions. Hell, I think some states have different ages for each gender.

Of course what is written in the lawbooks isn't always what happens in the real world though too.