There's a lot of factors to consider here. Are the tires original equipment? And if not, how are they different? Speed rating changes? P-rated extra load or just normal? Tires will tell you the max pressure and load. Extra load P-rated tires are usually 44 PSI max whereas the standard ones are 35 (there are some oddballs, like some Nankangs will be 36 PSI).
If you have OE tires, go with the owner's manual/tire placard specifications. Otherwise, if you've got cheaper tires on, you may want to add a little more air because they tend to be flimsier. If you have a stronger tire than OE, sticking with the manufacturer's specs on that is acceptable. But again, manufacturer's don't always have the best idea. As has been mentioned, some like to soften up the ride (GM in particular comes to mind. They tend to like 30 PSI in most passenger cars)
This also raises an interesting subject; the Ford/Firestone tire recall with the Explorer. I tend to believe that Ford was more at fault than anyone. They put P-rated tires standard on a 4,000+ pound vehicle. That's perfectly acceptable, but the tire placard in the driver's side door says to inflate to only 26 PSI! Getting away with that pressure on such a heavy vehicle would require an LT-rated tire, not P-metric, IMO. Otherwise raise the pressure. Also interesting to note is that I believe during the recall Ford was supposed to replace those tire placards with updated ones that read 30 PSI front and 35 rear maybe? I know the newer ones have that (note that Ford isn't the only manufacturer to recommend exactly 26 PSI for an SUV. Although most of the others that do recommend that are much smaller and lighter weight, like the Honda CR-V).
And then we could get into the pressures used in some trucks with LT-rated tires... Like F-350s, Chevy 2500 HDs, Suburbans... A lot of them will read something along the lines of 55 PSI in front and 80 in the rear... that requires at least a load range E LT-tire (80 PSI max). You certainly wouldn't want to goto 35 with these tires if you're carrying a heavy load!
For most FWD passenger cars, 32 PSI seems to be the magic number. Of course they are all different. But 32-35 is generally optimal. Although if you are carrying extra weight quite often (4 people or a lot of heavy stuff) inflating your tires close to the tire's rated maximum wouldn't be a bad idea.
And for the record, radial tires DO wear out the centers quicker if overinflated. I see it nearly every day. I had a friend who put nice new Pirellis (P6's, if I recall correctly) on his Eagle Talon and he way overinflated them. Within a month the rear tires had absolutely no tread left in the center.
