No I didn't say anything about unlimited ads - what I mean is that rather than say user 1 can have 10 ads - you would have user 1 in group a and group a has a limit of 10 ads. If the person subscribes to the forum they get moved to group b and that group gets 20 ads.
It's probably just splitting hairs - what I'm getting at is not making things user level but group level. I don't know how other forums software works but vBulletin has got it half right with a primary usergroup and secondary usergroups - in this case the secondary usergroup controls how many ads - so on my forum a secondary usergroup is called pClassifiedsA (this is set in vBulletin to have no permissions at all - the primary group gives permissions) - in Classifieds, I then say that pClassifiedsA can have 10 ads at a time - one ends, they can add a new one but never more than 10 going at one time.
I think if Classifieds 2 gets released without a limit on adverts, then it's going to be a mistake and it would require hacking - and that's something I've always hoped to avoid doing in Photopost.