It sounds from the explanation that was provided that the free users for your product contribute not only to customer acquisition but also create value through their contributions to the site. In this case, free may make sense for your software, as only you can weigh your infrastructure and support costs vs. the gain in marketing and usefulness of the product.<p>But your experience may not be common to many other businesses. If free users aren't contributing to the product other than marketing, it would come down to a decision of whether or not that goodwill was worth the added cost. It can be hard to measure that cost, but perhaps Twitter Analytics and web referrers can provide an idea.