Some people have asked how we choose which sites to display on that annoying but actually very useful bottom toolbar. If you want to know how useful, go to your web statistics and check traffic over the last day. You'll see a hundred or so extra visitors each day.
Web stats by the way are one of those remaining pro-only features, because they cost a lot to calculate. They are really useful.
Back to the story. We started, a few weeks ago, to calculate a "site karma" that measures how active a site is, in terms of number of members, recent edits, and so on. All the 120,000-odd Wikidot sites are then scored into a curve and the curve is chopped into six slices, with karma 0 to 5.
What is this useful for? It lets us detect active sites with a pretty good accuracy. If you look at the bottom toolbar you'll mainly see useful, active sites. There are a few anomalies like the sandbox (lots of edits, but not really a 'remarkable site', but they are rare.
We will, later, make site karma visible and use it as a tool for managing one's own sites (fast access to one's own high karma sites). We'll also use this to replace the 'Featured sites' section on the main page and perhaps a list of the top 1,000 sites.
So the bottom toolbar shows pro sites that have karma 2 or higher, and free sites that have karma 4 or 5. This are the values we're using today, we'll tune them to get the most interesting results.