Yeah thats true, I have Ninja Gaiden Sigma and Oblivion installed on my PS3 and they both take around 4gb each, but i'll never be playing more than 4 games at any one time, so if i have a lot of game date on my hdd, ill just back the older games up on another device. Well since oblivion for the ps3 installs on the hdd to greatly decrease loading time, it takes up 4gb. I can fit that on my usb stick or pretty much anything else I can think of and then just transfer it on my PC. Compatible media devices are increasing quickly . Pretty much all portable hard drives are increasing their space and cutting prices really fast. I remember when a 1gb usb stick was 80 pounds, now I can find 4gb ones for 10 pounds.

Or if you still dont have the little amount of money it takes to buy something very cheap like that once your disk space runs out, wich will still take a while mind you, you can always just delete the game data, keep the game saves and if a year later you feel like playing that old classic again, i dont think its much hassle waiting for 5 minutes for it to install on your hard drive.
I remember waiting for FFXI to instal, download the updates and then also install them, now THAT was a pain
That game takes like what, 20 gigs? lol

BTW, what games do you have?
I have Motorstorm, Oblivion, Ninja Gaiden Sigma and Resistance: Fall of Man