Although Lexicon compares favorably to Google Trends, it has some flaws. In our tests it had trouble with low frequency words (like "semantic") and also it choked on "web 2.0" ("Invalid term: web 2.0. Check that each term is a single word or two-word phrase, and that each term uses only alphanumeric characters"). Also, to compare apples to apples, Google Trends has a wider range of data - including breakdowns by region, city and language.

Here is an example of Lexicon:

...and a comparable trend map from Google Trends:

In announcing this new service, Facebook was careful to emphasize that no privacy violations have occured:

"We have a cluster of computers that count the number of occurrences of every term (for example, "juno") across profile, group and event Walls every day. The system strips out all personally identifiable information so that there is no way to track a mention back to a specific person. No human at Facebook ever reads these Wall posts, and Lexicon does not look at personal messages, invitations, or any other private user-to-user communications."

Overall, it's good to see Facebook mining some of the vast data that they have - but not stepping on sensitive privacy toes while doing so.