How will this petition work?

I recently got a mail from a friend. Inside was a petition to save the Brazilian rainforest. The mail contained a list of 235 names from around the globe, and I was asked to write my name down on it and copy the mail to all I knew. I could also read that the 400th person should send the list back to a given address.

My question is how will this petition work?

What puzzles me is that a lot of new lists with the same names are going to be sent to others. If some of the lists were going to get 400 names there would be many identical names sent back to the starter.

Lets say that only 5 people are going to send the mail out, and this continues until the list has increased with 20 new entries. There has now been generated 5^20 (!) new lists. If it would go on like this the mail-starter would not get mail at all. It is possible that a list might contain 400, but I think it is unlikely.

I remember a study made in Harvard that said something about how far a random person is counted like a friends friends friend etc. I think a random person is less than "7 friends away", but I don't remember that number exactly.