The same goes for other certifications. In general, all they show is that the person with the paper has put up with a structured course of learning that may or may not have any relevance whatsoever to the real world of whatever the subject matter of the course is. I've gotten a few professional certifications, but they've been only useful to cover cracks in the walls. The MCSE certificate is a notorious example of this: to pass the test, you need to learn stuff that's not useful in actually doing the work that MCSEs are supposed to be good at.
Even so, there's sometimes a need to get the paper. The current flap over the Texas VHF-FM Society is a case in point. The Gang of Three has posted an update to their site calling my parliamentary expertise (among lots of other things) into question. Since my National Association of Parliamentarians membership - for which one must pass a test showing one knows Robert's Rules of Order fairly well - isn't enough for them, I just spent $100 at the NAP store on study materials for the Registered Parliamentarian test. Whee. Once that gets here, I'll get to spend another $100 on the exam fee for the test itself. They cite a 40-day lead time for the test; that means I'll have to hustle to get it in before I go to Austin for the next meeting.