Greetings in the great lord's name. My name is Idi Akbar. I come to you as a request for help with have been trying to find records of efficiency of scambaiting. But all websites require money, and I can't access my money that I have received from a rich relatives inheritance. If you would be so wonderful and kind as to give me you bank account number, I can transfer only a few money to this bank, so I can access my funds. In return, I will find the research, and repay you with 5 times the amounts. This will be a quicks and safe transaction, so there will nothing worry about.
All kidding aside, I have been searching for about 3 hours, and I couldn't find any concrete data saying that scambaiting reduces spam as a whole.
It seams as though scambating works on an individual level. Usually a scambaiter will spend quite a long time wasting an individual scammers time instead of spending a short amount of time on multiple scammers.
From what I could find, it seems as though this is done much more for either entertainment of the scambaiter, or a feeling of "justice" when making a fool out of a scammer.
Amusements that the baiter may gain from the interaction include fooling the scammer into falling for claims just as ludicrous as the ones that the scammer is using to defraud his victims. Baiters will often use joke names which, while obviously ludicrous to a native or fluent English speaker, will go unnoticed by the scammer. Similarly baiters may introduce characters, and even plot-lines, from movies or television shows for comedic effect. It has also been known for the scammers themselves to adopt fake names that in their native culture would seem equally ludicrous. This reflects Western scambaiters using names from popular culture; in contrast Westerners would likely be unaware to identify with names that would be familiar with Nigerian or other West African popular culture. (1)
I have done this a few times myself using the name Jayed Garhoover (say it out loud a few times Jay Edgar Hoover....) with the FBI hotline as my phone number. It's actually a lot of fun, and can get quite amusing sometimes. (I've had them call "my office" and ask for me, I get the funniest emails afterwords....)
An example of the "longer, individual scambaiting" I was referring to is as follows:
A scambaiter named Mike Berry received a scam e-mail from a man in Nigeria who claimed to be rich and dying of cancer. The scammer wanted Mike's help, and of course, Mike's cash, distributing tens of millions of dollars to charity before he died.
But the man from Lagos wasn't dying of cancer, and his story wasn't true. Through a complicated chain of e-mails that lasted more than six months, Mike persuaded him to re-create the Monty Python parrot sketch, promising to enter it in a phony film contest with a cash prize. The resulting video shot to the top of YouTube's hit rankings, and has become an instant Internet classic(2).
The full list of his emails can be found here. It's quite long...
That case was extreme enough, but sometimes, scambaiters will go even farther.....
In February 2011, the Belgian television show Basta portrayed, with hidden cameras, how a scammer was fooled during a meeting with baiters, raising the stakes by involving a one-armed man, two dwarves and a pony. Eventually, a police raid was faked, during which the baiters were arrested and the scammer went free, abandoning the money, and without any suspicion.
However, while all of these cases may have humiliated the scammer enough not to do anything like that again (although I'm not entirely sure it did), this is on a much smaller scale than what would be needed in order to stop internet fraud all together, or even significantly cripple it.
As far as the "software that automatically baited scammers", it does exist. They are known as fake address generators.
Upon receiving connection from blacklisted spammer, rather than rejecting connection right away many servers would use tar-pit technique. Which means basically keeping connection open until it times out. The idea is, that SMTP is typically transported over TCP, meaning that single computer has limited number of simultaneous connections (open sockets) it can make. Thus, should spammers use standard SMTP server with standard settings, tar-pitting would seriously hamper their throughput. However, all of above techniques are completely useless when spammers use botnets.