Adding to the already great answers - which are all some variant of "it depends"... the "it depends" includes:
From Lucas Kauffman - it depends on your role - many certificationes depend on the role you're applying for. Some certifications apply to specific types of security roles.
From Eric - it's also the needs of an organization - a Cisco shop wants Cisco certs and so forth.
From me - there's also the business model of the company - these days, for example, the US defense industry requires a certain number of certified engineers for the bidding of certain proposals. So hiring (especailly at a senior level) individuals with those certs is a major bonus. In this case, it's not the nature of the work OR the role, necesarily, but a created context to show the customer the company's qualifications. I can imagine other consulting type businesses with a similar focus.
I'll even go so far as to say that when I'm reviewing a candidate's resume, I'll check whether the applicant is what I think of as a certificate "junkie". Since I often have weird teams that need to be very flexible, no one certification really does it for me... but I like to see that the person I'm talking to takes an active role in self-education and improvement. Seeing 1 certificate or similar education effort every 3 years is a good indicator. Seeing a set of alphabet soup long enough to write a novel with makes me wonder if the guy spends any time working! Usually I verify and follow up to see if there was a work context for such a thing - like a consulting role where the more certs the better...so the guy was funded to go nuts with self-study in the off season between consulting gigs.
I'll also ask "why this cert?" in the interview. Bad Answer: "Because I thought it was good to get a certificate, and everyone said this one was good for getting a new job." Good Answer: "Because the syllabus included X topic, a point I wished to know more about or thought might be a weak point in my current skill set... where I was looking to make a transition to < a role like yours > I figured I might need that." Note - whether or not the candidate is right about the needs of the role doesn't matter much to me... more that he was looking at what he really needed to supplement a weak point, and that he had a plan for growth. Bonus points either way - extra major bonus points if he's actually right about the role. :)