This article on Slate by Emily Bazelon gives a pretty thoughtful review of the arguments for making prostitution legal. My only quibble is with the last clause: "and Eliot Spitzer is really, really unlucky." No. Eliot Spitzer is really, really stupid. Because while I don't really care what the man does in his private life -- that is between him, his wife, and his demons -- the fact is if you're a public figure your private life is up for grabs. It's part of the trade-off. You want power, you want fame, your life becomes an open book. Second, it's not like anyone in public life doesn't know this. If you're in an elected office, to behave like this shows such blatant disregard for the things that matter to the electorate and the press and therefore it shows poor judgment and great hubris. And, of course, the great difference between Clinton and Spitzer is the former didn't pay for it. He broke the laws of marriage, but not of the state. Even if you think prostitution should be legal, if you're a governor, or just an average citizen, you should abide by the laws of the state you govern.
Otherwise, I'm saying nothing else about Spitzer. It's too local and enough else is being said.