Large Web sites will no longer have a monopoly on the ability to handle a large number of users. This is just an example of the kinds of things users can do when they band together. But it gets better. Once this starts to catch on, proxy servers and Web servers can be adapted to start participating in the system. Imagine a new HTTP response code that indicates that the server is too busy to handle your request right now, but that the data you want was just inserted into FreeNet with a given key.
Small sites get to leverage the bandwidth and storage of their users to reduce costs.
FreeNet itself benefits in a number of ways. Since many more people are using FreeNet just by using their browsers, the amount of information and overall storage capacity in FreeNet is increased by several orders of magnitude. All the virtues of FreeNet's design become stronger as the number of users increases. In order to be successful, I believe the WFW should work as a true grassroots user movement. In order to support this, the WFW will have to add slightly to the underlying FreeNet protocol.