There is no easy and efficient real person verification that would not be incredibly intrusive to the people who are interested in the products.
The current process is connected to a master spammer database, but while it has quarantined more than 15,000 applicants - it only takes a little extra effort to get by it with a new email address and new IP address - neither taking much time or energy. Despite that, the number of spam attacks that have gotten onto these boards have been minimal overall, and when they hit they are addressed rapidly.