Make sure none of your swap is being used..start everything you normally would and watch if swap is taken up. Then start Netscape 6 or Mozilla 0.9.X and see if off the bat at least 4M of swap is taken up.
If so..then it should be reported as a bug. Mozilla/Netscape shouldn't go for swap as soon as they are started and ignore the available RAM.
Ben, you seem rather obsessed with VM behaviour these days. ;) Using swap is not a bug. The VM doesn't just use swap when the RAM is full of process data; it uses swap when it can see a better use for the RAM. When you load a big application like Mozilla other processes may very well be paged out to swap if they haven't been used for a while. That leaves more of your RAM free for more useful things, like cache space.