While I give the author the benefit of the doubt he or she has every intent to respect privacy, if I really care about my own privacy I should do what I can to protect it myself before I place my trust in a third party.

It's like revealing my own secret to someone and telling them not to tell anyone else. I have the most to lose if my secret is revealed. If that isn't enough for me to keep it to myself what is preventing anyone else from revealing it?

Because I don't care to let people follow my browsing behavior site by site, I had better not broadcast it to begin with.

EDIT: I should add, I do have some initial doubts about the anonymity guarantees in this extension. Is all traffic encrypted? Can I be sure nothing is getting unintentionally logged by say a forgotten debug statement or server request logs? I've seen credit card numbers turn up in Apache access logs. Is my IP actually obscured from others or is it merely my name? Even Tor is hesitant to guarantee anonymity.