My opinion is “real-time visitors” is kind of a bogus number. What are you counting and what’s it supposed to represent. What about robots and abandoned browser sessions (open tabs).
Also on smaller traffic sites(like most RapidWeaver sites) the number of people actually on a page at one time is probably going to be tiny. There’s 1,440 minutes in a day, I often hear RapidWeaver developers stating they have 2,000 or so “hits” a day, you can do the math.
Not to mention the overhead added to accurately track something like this.
Doug, you raise a good point about what is being counted. With boring content on my sites (compared to the drama gracing BBC’s pages these days), a real-time counter would highlight how few people are on a page at one time.