This is an excellent add-on. It seems to work exactly as advertised.
I have a couple of suggestions for the developers:
1. Help users choose RSS feeds for generating queries. Different users have different requirements: To obscure bland search behaviors, mainstream feeds (like your defaults) probably work best, but to obscure more adventurous search behaviors, it will probably be necessary to add several "interesting" feeds to the mix. I just spent some time looking for unusual RSS feeds, and I found some good ones which I'm now using in TMN. If these feeds work as I expect, the search engines will soon conclude that I have dozens of remarkable (albeit contradictory) interests, and my true interests will be lost in the noise. Anyway, it was work to find these feeds, and if you were to host a forum for the purpose of discussing TMN query feeds -- or at least post a list of suggested feeds -- I think it would greatly help users effectively configure TMN.
2. Why not obscure browsing behavior too? Logging search queries is just one way Google (and others) keep track of us. Many websites report to Google the IP addresses of those who visit their pages. Thus, a good portion of our browsing behavior is tracked by Google, even if we never use Google to search. Fortunately, I think TMN could easily obscure browsing behavior in addition to search behavior. The program simply needs to remember some of the websites it visited as part of the click-through feature, then continue to visit those sites at semi-regular intervals. Please think about it.