The Exodus was great, but I think the greater achievement were the discussions we had beforehand. That was one of the first times I had seen the entire site involved in a decision and planning for the future of Iwaku. The eventual decision for the Exodus only came after 'our' (rory and Asmo's) request for complete control over the site was shut down by Homac, who at that point was inactive to the point of invisibility.
There has been talk of Rory running the site alone, but luckily Asmo decided to stay on, and Diana joined the team for GREAT JUSTICE.
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I wouldn't know the true statistics (ask Diana) But I believe roughly half the current active members used to be around on either AFTA or Moonwings, earlier sites made by Diana. The drive to join Iwaku began slightly before the exodus, but really got going when Iwaku got hosted on the same web-address as AFTA.
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The old Proboards site used to have an adult section which was password protected and contained shirtless pics (Asmo was one of the first to post, for all of you fangirls) As well as some private RP's, naughty games (guess the above posters fetish!) and serious mature discussions. It was ermoved after Proboards pointed out that it was against their TOS, which led to Member ridicule of the proboards terms of service, and the use of "TOS Violation" as a sort of censorbar for nasty stuff. For example: "I'm going to TOS VIOLATE you so hard that your TOS Violation will be the size of a grapefruit!" It has turned into an old injoke since then and is rarely used anymore.
The old adult forums are back though, in the form of Diana's membergroup "Smutclub." Check it out if you are over 16 and interested.