From my experience, whether or not you accept free email addresses from webmasters, the ONLY thing that will protect you from scammers is vigilance...and a little bit of women's intuition.
Ivy, by watching the webmaster, you caught him...tho I'd have been suspicious as soon as he sent thru 2 multi-month signups...that goes against the general surfer buying pattern for sure.
I had an article published in Klixxx regarding webmaster fraud towards the end of last year (or so I've been told...I'm yet to lay eyes on it

)
If anyone would like a copy, drop me an email and I'll send it by return mail.