With people saying they could lead to an income of $26m a year, or pay for all of our normal hosting costs in a fortnight, I'd like to know what these other reasons are!
It's purely speculation to imagine the income would be that high. From my experience with Wikicities, $26m seems an exaggeration. Also, would the number of people visiting stay as high if we had ads? Would there still be the same level of motivation to use Wikipedia.org as opposed to a much faster loading mirror?
The threats of forking and boycotts over the last day highlight one of the biggest reasons for not doing this, or certainly for not rushing into it - Wikipedia.org would be nothing without the community behind it. Would they still be behind it if AdSense was used on the site? Even if for just two weeks a year? Would we be jeopardising our non-profit status? What effect would turning Wikimedia into something commercial have on the project? Would it make people less likely to donate / less likely to use Wikipedia / less likely to edit?
We also need to bear in mind that covering the basic costs is only the beginning. Our goal, of providing free knowledge to every person on the planet, is a much larger aim than buying servers for Wikipedia, and 2 weeks AdSense isn't going to cover it. Would those 2 weeks prevent us getting the grants, donations, corporate sponsorship, and volunteer effort, needed to attain those wider goals?
These are more questions than reasons at this stage, but the fact that so many questions exist is a reason in itself not to even consider this until they can be answered.
Angela.