Exponential growth continues, both in the number of users and the amount of traffic.
With trends like these, it is almost certain to get worse before it gets much better. A number of different factors can make Web browsing slow. Internet circuits in many places are running at full capacity and often suffer from congestion. Since a typical Web transaction involves a handful of service providers, any congested link along the way can cause the entire connection to be slow. It might be your local provider, a backbone operator, or the remote server's provider.