not to mention that in typical PSN (SEN) fashion, a demo is the size of the full game in most cases. Which is fine if you decide to buy it, but a nightmare if you just want to try it. A few of those will fill a card real fast.
After getting a 30 mb update for hotshots, uncharted demo (not full size, 8xxmb/3.xxgb), rayman demo (full 1.5xgb), the 3 a.r. apps, and netflix the 4gb card is nearly full.
If they ever do map packs as dlc for the future killzone or COD titles, the 4gb will be obsolete. I mean I remember when a 512mb card for psp was more than enough, then cut to Metal Gear or some such game that were nearly 2 gigs