Brad Burnham writes after a meeting with Craig Newmark of Craigslist:
Customer service is the new marketing because you can realize the radical efficiencies of the web only by enlisting the users of the service as co-contributors. The best web services provide bandwidth, cpu, storage and a governance system and then their users create the service. This is certainly true of Craigslist but it is also true of more commercial implementations like YouTube, Flickr, and del.icio.us. So if your users are your co-contributors, your co-creators really, what does it mean to sell them?
If you need to convince your contributors of the value of your service you have probably already lost. All of the web services I mentioned are free, so selling them doesnt make literal sense anyway. What you can do is serve them, and serving them is the best marketing you can do. Why, because only by serving them, can you learn what it is that would make the service more useful to them.