Is the forum only generating revenue from donations now? Doesn't seem like a viable business model.
The forum has enough budget/reserve for many years that funds getting from forum ads is unnecessary anymore.
With the mixers issue and selective scamming of gambling sites, since these two are the most service who get ad slots here, it really make sense theymos stopping forum ads being undecided on what service he will accept.
It's better to strike a deal than an auction type so the forum can choose the kind of ads that is suited for the Bitcoin community, Bitcointalk is so huge that a project or company can easily get massive leads if advertise here in Bitcointalk, they can easily get long term advertising contract because Bitcointalk is here to stay for a long time.
I hope they can still show ads but for projects that are suited to what they want to show, we should be thankful that Bitcointalk is supporting its members even though there are no ads for revenues.