Very Spatial notes that MapQuest is 21st in Alexa’s rankings of popular web sites, which sounds impressive for a standalone map site. But, a couple of caveats. One, Alexa’s methodology is kind of like the Nielsen ratings — it gathers its metrics from a user-installed web browser toolbar. Two, from what I can glean, subdomains are measured as part of the main site, so the numbers for maps.yahoo.com, maps.google.com and local.live.com are folded into their parent domains (#1, #2 and #12, respectively).