Yeah I totaly agree, swarming is far far future.

Before swarming other concepts for reducing traffic are more important IMHO: query chaches, super peers (!) and a substitution for ineffective ping/pongs. This stuff will hopefully dramatically reduce backbone traffic, and e.g. modem users can download with full speed.
Another interesting approach to reduce traffic was not mentioned here so far: Host caches or super peers with a regional toplogy and multicast, to reduce ISP traffic. While gnutella backbone causes huge traffic for ISPs, traffic should not be reduced inside gnutella network only but also for the underlying physical network. Not reducing this huge ISP traffic, means slower network performance and increasing costs for ISPs. This could mean for the enduser (us) increased internet costs or more expensive flat rates.

About your question for caching/swarming most requested files. I don't know how to describe better... hmm. Swarming means to solve one basic problem of gnutella: busy slots and only few people sharing. The problem could be solved by spreading often requested files (NOT seldom queried files) over the network, so downloads will be happen more often and much faster. If you have any further question, just ask here again or meet me on IRC.
It would be interesting if the Limewire developer would describe their plans on swarming. Anyone knows details?

Greets, Moak

PS: Super peers are mentioned in this thread