I am aware of the current “certification is evil” line going through the software testing community. I have to say that, I don’t agree with this line.
As user246 mentioned, people do occaisionally attain this certification to be more marketable. People also often sometimes take this certification early in their careers in the hopes of learning more. Certainly not going to hold it against them.
To your question however. Certification does not prove that someone knows how to test. They can show that you have learned a set of “common” terms and idea’s. They may even teach someone some of the basics of testing, however, really good testing can only be learned through experience, practice, and personal retrospectives as to what they actually learned while they were testing.
If you want to put the time and money into them, I certainly wouldn’t begrudge you for having them if I happened to be interviewing you, I’ve often contemplated the same thing myself. There are managers however, who feel that certification is a requirement. In this case, if you are in a very competitive market, it could very well help give you a one up over another candidate.