LKML (Linux Kernel Mailing List) is one the busiest mailing list on earth. It's a virtual world where many Linux kernel developers joined and gathered to discuss things about Linux kernel development.
So what do you think when many people gathered around? There's a big cake for spammers to put their spam messages to whole people joining the mailing list and there you have it. Check this out (i hope it haven't been deleted or banned).