I´m not an expert after all, maybe you should talk to Alrik, he came up with this. As far as i know bots are programs that search for unprotected users in order to misuse their E-mail addresses, and or send them spam, or even try to figure out passwords which could be the same for your bank accounts...
Yes i know what it is but i did not know the english word.
In french bot is "moteur de recherche".
It is sure that they use the mail addresses in the forums for sending spams.
And Alrik is probably right saying that some of them try to steal private informations to the users.
Barta