There have been many times over the years when someone has asked me to assess someone's skills. Usually this is by looking at a CV, but it has also involved talking to them in an interview setting.
For any potential employer, the hiring process is painful. They know they need someone, but typically they don't really know who they need. Could be they need to hire someone to join a team, in which case they can ask the team what kind of person they would like. But often they just know that they need someone to do a particular job.
First step, they need to write a job specification. Great. What they really want to write is "We need someone to be able to fix up this stuff" – but they actually have very little idea about what skills may be required for that. So they put criteria like "Must be good with people" and "Must have experience in the integration of systems". But really, they have very little idea.
Let's suppose somehow, they get a terrific advert written up, and the CVs start flying in. That's a really good start. Now they need to go through those CVs and work out which of these people they are going to invest their time in. Getting someone in for an interview will take time. There's the interview time of course, but as well as that, there's arranging a time that suits, and working out a range of questions that not only suit the role, but suit the candidate. They might want to ask about the candidate's time abroad, or why they left that job which sounded so good. All-up, I would guess that a single hour-long interview would take around 3 hours of effort.
So you can't interview everyone, you need to use CVs to filter them out. That's tough. You try to rank them according to a feel for whether one is better than another. But how do you do that? Is this person who has worked for a couple of big name consultancies better than that person who has a degree from a top university? Does it matter that this person has a few gaps in his CV? Lots of questions need to be considered.
Typically as a candidate, you need to be able to demonstrate very quickly that you are better than the crowd. Obviously if you have an outstanding employment history, have written books, that type of thing, then you may get through on reputation alone. But if you have a good reputation, then you're probably not applying for jobs anyway – the employers are probably chasing you directly. For the rest of us, it's much harder.
Certification can help I think. If someone gets two identical (-ish) CVs across their desk but can only get one in for an interview, does it help that one has achieved some level of certification? I think so. Does it help that one is a member of a professional society? I think so. It doesn't mean that the candidate is necessarily any better, but it ought to increase the odds of it. The person without the certification might not be good enough to get certified. Or they might not qualify for membership of a professional society. So I think employers will always lean towards the person who has these things.
When you get a certification from Microsoft, they send you a certificate in a folder. The folder says "How they know you know". And I think this is the key. Whilst certifications don't guarantee you know anything, I think they do go a long way. And after all, even if it's more like "How they can justify hiring you rather than the other guy", then surely that makes the certifications worthwhile.