Movies, TV and MP3's would EASILIY fill the 15(ish) gigs available on a 16gig card. Now, if someone was able to make a fast emulator on Java (doubtful) you would then have to load roms too. Now add apps (assuming we will be able to install on card- if not, the market will be doomed) on a card, and you will be yelling for a 32gig card.
You non-media types kill me.