Email can and does get diverted to spam filters or deleted by ISPs. If you didn't see the email, you should check your spam folder. I got the email 5x (once for each of my accounts). If you don't bother to log in to the boards where it has been posted since May 20, how is Auctiva responsible for that? They made the information available in a variety of places with quite a bit of advance notice - if you didn't happen to see it, I don't think they can be blamed for that.
Almost all monthly services with a set monthly fee (i.e., Netflix, Ebay stores, online gaming, etc) bill a month in advance. This is a one-time thing, then it's on the new schedule. In addition, if you've got an AucCom store, they've continued to postpone the date when they will begin charging for it - don't think you can complain about that!