The forum is not a charity. The forum is run in order to improve the chances of bitcoin succeeding over the long term, along with furthering the forums stated mission that loyce quoted above.

I am not surprised that forum suspended ad auctions. Given the obvious process of having to manually vet each new potential advertiser, and the low auction price in recent months, selling ads was likely not worth Theymos’ time for a long time.

I think part of the reason for the low ad prices is strict requirements to advertise, and the long list of things that Theymos won’t advertise. Plus, the forum doesn’t offer any kind of targeted advertising, which is something that advertisers are offered almost universally. The lack of targeting means more privacy for forum users, and that is the price the forum is clearly willing to pay in order to offer privacy.