the blockchain right now is not 600mb, its more like 400, excluding the index files. and that can be compressed to at least 80% of the original size.
and. 16 gigs should be good for a linux install and 2 more years worth of blockchain worst case.
It is my understanding that the nodes save multiple copies of the block-chain in case of a split or one of the block-chains becomes the "longest" one. I have had a test-node running since June 9, 2011 (0.2.22 and 0.2.23) for a total of 55 days. It ran out of disk space today; consuming 5.8 GB. That works out to 105MB per day. Disk usage dropped to 4.9GB when the client exited. The client had 125 connections during peak times.