So we've probably all read over Kevin Kelly's idea of 1,000 True Fans - I'm putting up a link to one of his posts on the subject here:
http://www.kk.org/thetechnium/archives/2008/04/the_reality_of.php
So, the question to you all: would you like to have only 1,000 'True Fans' of 1,000,000 'casual users'?
I'm calling the fans those who would pay to use your site, maybe once a year or once every couple of years, and communicate directly with you about your business. The more passive 'casual users' would use your service for free and communicate very little with you, if at all, about your business.