Who said I was running Windows?
You're right though, don't be stupid and buy 4 Terabytes of RAM for your iBook if all you do is use iChat and safari.
But I've come to notice that when a user complains that his machine is too slow for a task it's often because the said task is memory intensive, such as opening a 100megs photoshop file, or adding more than 5 tracks to GarageBand... Such operations are greatly relieved by gobs of RAM.
Being a developper of my own, I can't stress out how much RAM I need. Java anyone ?
And when I need to run VirtualPC, well... thank GOD I'm not swapping.
Throw in resident apps introduced by Fast User Switching (my girlfriend always leaves FireFox, Word, Thunderbird, Excel and iTunes on while FUSing out
)
And don't get me started on games
Bottom line is -for me- if your machine is a tool for your job, don't let swap get in the way of your work. A pleasant computing experience does make you more productive.