Limewire relies on the host OS management of TCP. At least on linux that is totally unfair and if bandwidth throttling is enabled, one fast downloader will monopolize the entire available bandwidth - we've observed situations where one upload is going at the maximum allowed bandwidth and 19 other uploaders at 0KB/sec. The same is likely true for windows and mac osx since everybody uses the NetBSD tcp stack anyways.

Whether this is a real problem in the network is debatable because everything works fine when bandwidth throttling is not enabled or is enabled but the limit of simultaneous uploads is small (<5). Vast majority of the users out there will not have that enabled, and the few that do will most likely also limit the number of simultaneous uploads.