Here are my two cents.
I can see Mark's point about certs not being guarantee that a candidate is skilled. I believe in the value of certs, but I once phone screened someone with BrainBench cert who had no idea what they were doing. Even so, I can see some values to certs specifically in relation to the hiring process:
1) If you are involved in hiring somebody, and have the cert, you really know what kinds of questions
you should be able to ask the candidate. If they can't even display the knowledge documented by their cert, they didn't learn much from the experience. I'd have strong doubts about any other skills they claimed too.
2) Some jobs advertise specifically that they want the cert. Obviously you are in good shape in these cases.
3) In times of high unemployment when you are hiring you wade through a lot of junk resumes. You really can't read them all. Those little cert acronyms catch the eye. They don't get you hired just by virtue of having the cert, but maybe they stop your resume from hitting the circular file on the first pass through the pile.
4) If you have a cert, and the person interviewing you doesn't, it might be an interesting discussion tool. If they ask you about it, you should be able to tell them how the cert helped you, or didn't help you, to become a better developer.
5) If you find somebody who is truly unconditionally negative towards you just because you have a cert, you just got the best piece of data you ever could in a hiring process. You don't want to work there. They've just pre-judged you on a piece of trivia without bothering to find out anything more about you. Odds are that they are like that about other things too. You really don't want to work there, but you got to find out the bad news before it was too late.