Been doing a few interviews lately. Here's my take:
The following things values are logarithmic or exponential (depending on the case), not linear:
1) Page count -- One page isn't a hard limit anymore. Your resume has to go through keyword systems and spends most of its HR/recruitment life as a .doc file. The computer doesn't care and you're not getting graded on making it an appropriate length.
2) The value of the words on each page -- Make your first page count. I try pretty hard to read the first page or so but start to lose interest as things progress. If the resume reads like a monotonous diary of your activity over the last two decades, nobody's going to be able to tell which words they should read and important stuff will be glossed over.
3) The age of the experience -- If you did something really excellent more than five years ago, definitely include it, but you should allocate more space to more recent experiences. If you have three bullets each from your last three jobs and eighteen bullets from the fourth most recent, you're going to look like you have no career inertia or that you're just looking to park. If you have ten years of experience you can skip the details of what your college jobs were -- if they're in field include enough information to show how your career arc builds, but recruiters won't care about individual accomplishments.
4) Accomplishments, not tasks -- Your most recent job or two should show a few tasks but an overwhelming bias toward things that you actually did. A list of tasks you were charged with just shows what you didn't like doing enough to continue doing it. The balance should shift as the experience ages -- maybe 20/80% tasks/accomplishments in the first job, 10/90% over the next few, but blending back to 50/50% or even lower as the experience ages. Again, the older or extra-field ones should be especially short.
Personally I try to walk the walk on these points, and I also maintain a couple different versions of my resume. The version that I put into the job sites has a "products used" section near each job to pander to lazy recruiters who put "solaris" into the search box when they need a UNIX system administrator. I generally do not prefer to use these resumes after making contact with the recruiters, because no human cares what versions of SQL server I touched at a job five years ago.