When I first started blogging in 2002 the aim, as much as there was one, was to cultivate a particular following. But almost immediately Randall Parker noticed that traffic to his weblogs were driven not just by conventional blog readers who became "regulars," but also transient search traffic. This is particularly common in the case of time insensitive posts. Basically there are two classes of "readers," the "one off" sort coming in through search engines, and "regular readers," of whom commenters are the tip of the iceberg. Here are classes of number of visits per visitor over the last two years at this weblog. I've log transformed the results. Notice the bimodality. If you care, currently it looks like the regular repeated visitors, as defined by showing up at least more than once a week, number on the order of 20,000-30,000.
