Should freelance writers use pen names?

Oooh, I get this one a lot!

I used to kind of think using a pen name was a chicken exit - you didn't want to be associated with your words, so you copped out and went worse than anonymous.

But there are lots of great reasons to use a pen name. Here are a few:

1. You're getting into info marketing, and your niche markets cover a wide range of topics. Can you really be an expert in bird houses, wake boarding, sushi, and coin collecting? Maybe - but you might want to use a pen name so you don't start looking like a jack of all trades, master of none.
2. Your client wants you to post articles for them, but doesn't want their own name on it. Again, a good reason to use a pen name. I had a client in the furniture business like this, and again, I didn't want to dilute my own name by publishing myself as an expert on antiques (which I'm not!). He didn't want his name on the articles, either, because he wanted them to look more journalistic than self-promotional.
3. You could write for a niche that's kind of sensitive. I listened to a webcast with one of the most successful dating tips site owners out there. She used to write under her own name... until she had a stalker! Now she uses a pen name.