"All that is gold does not glitter, Not all those who wander are lost."
You know those meltdowns we've had on this mailing list about userboxes? And fair-use images? And linking to harassment sites? And any other of the little issues that good Wikipedians everywhere are ready to drop everything and take a huge, noisy, principled stand on? Take those all, multiply them all together, square the result for good measure, and you'd have some vague shadow of the amount of outrage that would be generated if Wikipedia went and started running advertising at this point.