closed prophecy-i.com - developed counters site appraisal

[drunnells]

Does anyone have any opinions on this developed, but neglectged site?:
http://prophecy-i.com

And a stats page:
http://stats.prophecy-i.com/prophecy-i.com

Its a counter site with 4500+ registered users, though I doubt that all of them still actively use this service. The counters displayed on the users site will randomly display an advertisement, the idea being that I would be able to sell ad space one day. I haven't put very much effort at all into this project in years, nor have I made any effort (that wasn't half assed) to make any money from it. If I were to try to sell this site, how much do you think it would be worth? I'd like to hear I could make a quick buck on this one, but If that isn't feasible, maybe there are some suggions on how to profit from the counters/guestbooks? Seeing as the ads are displayed on other people's sites, not necessarily mine, how well could something like Adsence work, and isn't it most likely against the agreement to display the same ad on many sites?

Thanks in advance for any feedback!