Infoworld:

"Kontiki DMS 2.0 injects servers into the grid to manage and secure traffic. The servers watch grid nodes and try to arrange the best available connection based on each machine's CPU and network load. Every file transfer request queries the DMS directory server to identify the node or nodes best equipped to serve the file. That sounds like load balancing, but DMS 2.0 does the job on the fly. Kontiki's KDM client software will switch to a faster source in mid-download if such a source appears on the grid. If a node that was serving a file falls out of the grid, DMS swaps in another node and allows the transfer to continue uninterrupted. One client can pull from multiple servers to shorten downloads and improve reliability."

eDonkey lets you download a single file from several sources concurrently (using file hashes, not their names). Users keep connecting to and dropping from the network, you just keep queuing to new sources as they appear. There's also an upload throttle to keep some of your bandwidth for other uses, and download speed is capped as a factor of whatever you assign to uploads (up to 10KBps, beyond that threshold you get unlimited download rights).