It possible to run with only swap space. (Boot from a CD/USB of course!)
Make a 2GB (or however large your file-system is!) swap space.
Mount a tmpfs and tweak its number of nodes and size ("man mount" is your friend here!).
Copy all your files to this tmpfs. (This takes a while....).
pivot_root/chroot to this tmpfs and run from there!
I believe the recent Knoppix has a "toram" boot parameter that allows you to do something similar.
This gives a completely "ephemeral" system---switch off and its gone!
On the other hand you could also run disk-suspend to switch off power without losing the system.
Ext2/3, Reiser, JFS, ... who needs them?!