Designed Obsolescence.
You didn't really think they'd support this thing through 2009 did you? Oh, go back and read your EULA. It clearly states that at the start of 2009 you'll have to pay a subscription fee for you unit to continue working. You signed it in blood from the paper cut. Legally binding in hell.
In England if you are an amazing author you get Knighted and recognition of your entire nation.
In the United States you get lawsuits.
Someone looking up plumbing finds an ad for plumbers...
Someone looking at the London listing finds hotel and air travel...
Someone looking up nukes gets an ad for the FBI...
A simple google ad, text only, wouldn't kill off anything that Wikipedia is trying to accomplish.
However the idea of paying people to moderate, edit, or create articles is a horrid idea. The reason I trust Wikipedia is because it's run by the commons and while they don't get everything right, they get more right than most encyclopedias and with a lot more volume.
If they start paying, I'll just branch it for the free editing.
Keep to your strengths Wikipedia. You have good information that people rely on daily. Having a small text ad wont kill that.
Unlike projects by for profit organizations there's no need to continually create new versions of projects. Perhaps the dwindling developers is actually a great sign that the project has reached it's goals. Personally I think it works just fine and I can't think of any "new" feature creep I'd like to see added.
I know people who still use Word 5. Why? Because it was done. There wasn't a need for anything else. Maybe some bug fixes.
Are you using it?
Is it missing anything? (if you say yes... then you should really go add it.)
It's a naive, domestic operating system without any breeding, but I think you'll be amused by its presumption.