Matt's FormMail has many problems, but one of the biggest is its lack of security. Any instance of FormMail can be used as a spam gateway, because FormMail uses hidden form variables to specify recipient(s) and message subject. Do you want your forms used as spammer tools? Sure, FormMail checks the referrer--but referrers are trivially faked, and this is *not* good enough protection.
We need a good alternative to FormMail. I think (bias) that STAMP can be such an alternative.
I don't think that STAMP is the only possible alternative, of course, and it's possible that it wouldn't even be the best solution for FormMail users. It requires the use of CPAN modules, for example, which could be a possible turnoff to users who just want a simple form mailer. And it's not even the only alternative (I'm thinking specifically of Not Matt's Scripts, here).