Having a certification, if nothing else, shows a willingness to:
a) Either learn the material on the job or study to learn the material.
b) Be measured by a "standard," regardless of how you feel about the standard.
When I have participated in interviewing personnel, I always keep those two things in mind. You're right that having a cert isn't a guarantee that a candidate really knows his/her stuff. That's what a tech interview should reveal. But there is some credit in my book if the candidate has at least gotten some level of certification.
Loner, I get what you're saying, because as far as Microsoft is concerned, I have an MCP, MCSE but those were from the SQL Server 7.0 and Windows NT 4.0 days. I don't have an MCDBA, focusing in recent years on security related certs (Security+, GSEC, and hopefully soon, CISA). However, I would hope that my lack of an MCDBA would not disqualify me from a position. With that said, if it does, I do have the capability to do something about it: go complete it.
K. Brian Kelley