Nobody likes ads, but I also don't think I can demand someone provides a service out of their own pocket. Reading the announcement, though, the real issue is that the content is licensed CC-BY-NC-SA. He needs to relicense all the previous edits to be able to make a profit.
And yeah, quitting your day job to work on a wiki for a single video game is a bit crazy. But maybe he was thinking of leaving anyway, and has other plans for the future.
