I agree with Jen on this one: if it was a 16 year old boy a 28 year old woman met somewhere in a park, well, I think it's wrong and more than a little icky, but for the most part that's their business. However, when someone in a position of authority, someone you have entrusted your childs well-being to takes advantage of their position, they need their ass handed to them.
I dunno about the maturity thing, especially now that I'm on the wrong side of 21.
I think it's more of a priority thing, and that males and females don't see eye-to-eye on things. 18 year old girls can be the biggest drama queens, everything is CRUCIAL, and their man better be where they say, when they say or the world is ending. Guys? Meh, from what I remember at 18, give them some ass and some sports or a video game and they're fine (I'm probably way off base, but I'm talking more "perception" than absolutes).
When it comes to male teacher/female student v. female teacher/male student, I really think you have to take the societal stereotypes into account.
Young females are percieved as "weak" and "easy prey" on the whole, both physicaly and emotionally. Your 16 year old daughter can get knocked up by her teacher.
Young males are seen as "tough" and "horny". Your 16 year old son nailed his hot teacher, and he can't get pregnant.
Right? No. Fairly true? I think so. That's where the inequity comes from. So much for justice being blind....