I can't see how no one mentioned this.
It's not real at all. At all.
It's just a way to build an up to date spam list easily and by "hiring" volunteers that think they are helping a research project about what... oh, right, an University project for stats about what percentage of e-mails are chains! So how the hell are they going to get their percentages if you are only supposed to forward them chain letters? I mean, they'll get a 100% ratio.
Simple: you forward them a chain letter with your friend's addresses, your friends' friends' addresses, your friends' friends' friends' addresses and so on typed just nicely in plain text right there in the "to:" and "cc:" fields of the quoted messages. They parse the emails they receive, grab all the addresses, build an all new spam list from all your friends, friends' friends, friends' friends' friends, etc. and, hopefully, in a month send this very same request to all those addresses as well. Another chain reaction starts, with the result being them getting a fairly good quality database of people who are screaming to receive advertisements. After, em, of course, graduating from that fabulous university that studies e-mail chains *cough*