Compare this to InternetRelayChat (IRC), for example. There, you know the nicknames of people online, you know which nick said which words, you know who is participating and who is lurking (cf TheAudience). The same is not true for a wiki. On a wiki, you can find out who edited a page and when, but only indirectly, and you cannot find out who has been lurking.
RecentUsers is a feature that shows who has been lurking. If the wiki host wants to know who is reading the pages, he looks at the logs. The idea of showing this list to the readers of the site is not new. Many sites have a list of recent visitors, or a list of people "currently online".
For UseModWiki, a patch exists: UseMod:RecentVisitorsFeature. The EmacsWiki has the patch applied. See the following link for an example: http://www.emacswiki.org/cgi-bin/wiki.pl?action=visitors
Note that only lurkers with a UserName are identified, the others are lumped together as "Anonymous". The reasoning is twofold: I don't want to invade people's privacy too much, if they don't have a UserName, the next thing would be a reverse lookup of their IP, such as used in RecentChanges. I feel that is too much to ask from lurkers.
But, Whether that actually helps to build an OnlineCommunity is doubtful, however, since the only interaction is via page edits, such that RecentChangesJunkies get to interact in a very limited way, and the others do not. AlexSchroeder atests: