I can say I've watched people recieving resumes throw away all pages after the first without looking at them. Generally, if your experience is such that you cannot fit what's relevent it on one page, you're probably well enough known that you don't need a resume.
Yeah, someone like Steve Jobs or Bill Gates doesn't even need a resume but they could easily get any job they wanted with a business card-size resume, effectively listing their current position only and nothing more.
One-page resumes work fine if you're in a narrow field or if you've stayed in one career path all your life and you know that the people who are hiring will know everything that's entailed in the positions you've had.
But if you've worked in unconventional fields or if you're changing careers or applying for a job that's not quite like anything you've done before (my favorite kind of job to apply for), some job titles require a bit of explanation. For example, I've worked as an Expedition Coordinator, a Program Manager, and an Assistant Director (a job that was a total misnomer as I didn't manage anything but was really just a grants and contracts negotiator). I find it helps to provide a fairly detailed but concise description of what those jobs entailed to help employers look for experience and transferable skills. And depending on how many past jobs you list on your resume those explanations can push your content over a page.
I do have a one-page resume that I send only when people specify a page restriction, but I think I've only ever used it once or twice in my life.