I don't require an introduction on my site. Some people don't like the spotlight and I respect that. But I think it's getting more and more common. I had a guy the other day make a post in the intro forum saying "thought I better make a post before somebody deletes my account"... that was his introduction. I laughed a bit at that one. Personally, it's my opinion that some people may view requiring an introduction as a barricade and as a result you might end up driving a potentially really good member away.
Agree with all of the above, just irritating really when you have to post somewhere else just to post what you joined for all along.
One of the sites I visit has a banner saying "Have you made your intro?". Not forced to, but can't get rid of the banner unless you do. Members from 3 years ago all the sudden make there first post with the words "And not the banner is gone..."