I am not a part of the TechTracker development team, but asked many similar questions prior to its official debut and will try to address your concerns as best as possible.

1.) No. The index is uploaded to Cnet's servers for analysis (determining what software is installed, out of date, etc.), but it is not made publicly available.

2.) It can, if there is a specific flaw in the version you have installed, but the risk is minimal. And since TechTracker does not make your results public, the risk is averted.

3.) I would consider Cnet trustworthy and the risk minimal, but yes, there is a slight privacy concern since the information is being sent elsewhere.

4.) Cnet does not distribute user-specific information to third parties. Rather, if they do choose to use the information for business activities, they do so in aggregate form. Thus, they analyze the results from all of TechTracker's users and then tell the third party of important statistics, such as "95% TechTracker users have Internet Explorer installed, but 69% have another browser installed as well." (Example only; not factual statistics.) Your name, email address, computer specifics, etc. are not freely shared.

Hope this helps,
John