It appears, b!X pointed out, that “Joe Lieberman is advertising his website by hitting unrelated websites to which it does not link, passing along false referer information that points people to the joe2004.com website.”
“Doc Searls Weblog [1]”
I've checked my own referer logs for this month (January) and I haven't seen the Joe Leiberman referer spam, although I did see Wesley Clark referer spam (I guess if it's good for one, it's good for the other) and plenty of sites hawking the Paris Hilton (although why the Paris Hilton needs such advertisements is beyond me—are they going bankrupt there or something?). And in an incredible display of tackiness or cluelessness (or both!), I got referer spam from StarProse Corporation [2] which has an article about how bad referer spam is [3].
And Andrew Jackson [4] is still the most popular thing being linked to here.
[1] http://doc.weblogs.com/2004/01/03#sayItAintJoe
[3] http://starprose.com/modules.php?name=News&file=article&sid=44