Parapunter: You won't be surprised that I disagree with you.
By getting them to waste their time people who do what I do are keeping them away from other victims who might be more gullible. Also if they make repeated hits on real bank sites using the false information that we have supplied, they are more likely to get caught or at least have their activities curtailed.
It is true that we are encouraging more spam, but it's again a far greater waste of their time and resources than of anyone else's, and they will soon find the emails they send out being rejected.
If, hypothetically, everybody were to do this, and they realised that 100% of their time was wasted, their would be no more spammers or scammers.
Finally, winding these people up and looking at their responses (Nigerian 419ers specially) is a a great way to pass time, and if you don't believe me, take a look at some of the sites like
419 Eater - The largest scambaiting community on the planet!