Note: This is a preliminary essay, intended to give you food for thought. Comments are welcome, but at this time, please make your comments to me privately, or if you must be public about it, do it on the wikipedia-l mailing list. Everything discussed here is so preliminary at this point that public debate isn't really warranted. I seek feedback here primarily to refine my own thinking about the issues raised.
Someday, there will be advertising on Wikipedia. Either that, or we will have to find some other way to raise money, but I can't think of any.
This is not coming soon. As of today, November 9, 2001, I would say that this is at least 6 months to (more likely) 1 year away. Why then, and not now? Because despite encouraging growth in traffic, the amount of money that could be made from having sponsorship of Wikipedia is not enough to worry about.
I imagine that there will be some resistance to advertising from adamant anti-capitalists, and from those who think that any association with money is necessarily corrupting. I can't really help that, and I can only state for the record that I think such people are seriously mistaken in many aspects of their world view.
But there may be other resistance to advertising from people with legitimate concerns! And I hope to address those concerns now, long before this becomes an "instant issue".
First, I know from long experience at Bomis (which currently has more than 100 million monthly pageviews throughout our entire network, which makes us a big site, but not exactly Yahoo!), that advertisers don't ever attempt to dictate content. So it strikes me as extremely unlikely that any advertiser will ever care what Wikipedia's content is. Certainly, I have never seen it at Bomis.
Second, despite the fact that such a thing would be extremely unlikely, if an advertiser ever did ask for changes to the content to flatter them, I would simply respond: go to hell. The independence of the community is essential to the longterm success of this project.
Third, advertising should be done in a tasteful way. To me this means at least these things, and a lot more besides: (a) no popup ads, (b) advertising clearly marked as such, so that visitors do not mistake it for content, (c) keyword-based advertising to whatever extent possible, so that the user is presented with _relevant_ advertising, (d) text-link based advertising preferable to banners or other high-bandwidth advertising, to preserve the beautiful simplicity of our interface.
I will add principles to this list as I think of them, or as you suggest them to me and I accept them as valid.