If Google (NASDAQ:GOOG) isn't ready to rule the world, it may as well settle for the World Wide Web.

Last Friday, the leading online search engine launched Google Trends for Websites, a free Web-based tool to gauge website popularity. Enter the name of a popular -- or even modestly popular -- website into the box, and Google spits back geographic usage data. For instance, did you know that according to the Google app, The Motley Fool gets more visitors from India than from Canada? Well, now you know. Sort of.

See, Google doesn't have exact information. It uses a combination of its own search data, third-party research, and information from opt-in webmasters and Internet users. In other words, the results won't be perfect -- but the same can be said of existing site trackers such as Compete.com, Amazon.com's (NASDAQ:AMZN) Alexa, Experian (OTC BB: EXPGY.PK) and comScore (NASDAQ:SCOR).

Google's site also lists the most commonly visited secondary sites, as well as the search queries of visitors to that domain. Those tools may be useful for webmasters who want to find other sites to partner with, and for visitors who want to discover related destinations.

An interesting aside: Google generates trend overviews for all but the Web's smallest sites, but it also omits Google-owned sites, including Google.com, Blogger, YouTube, and social-networking site Orkut.

What's up with that? Google has no problem releasing the data from rivals such as Yahoo! (NASDAQ:YHOO) and Microsoft's (NASDAQ:MSFT) MSN.com, but somehow its own cooking is a trade secret? If I were a little more cynical, I'd wonder whether this stance skirts the "don't be evil" mantra that Google once adopted -- yet occasionally strays from.

From a business standpoint, the data from the world's search leader should be relevant. The site should also attract webmasters, which it can then win over to its Google AdSense paid-search syndication program. It also doesn't hurt to butt heads with comScore again.

Google got the better of comScore back in April, when Google's blowout results were far better than what comScore's online ad trends were predicting. Let's see whether Google scores another punch now -- and whether it's a clean hit or a dirty one