If the site contained a strong privacy guarantee on the front page -- basically, no data about individuals' surfing habits will be stored, but aggregate data about overall traffic will be stored unless you opt out -- I would use it if I needed it.
I understand this would raise red flags for a yc type crowd.
Would the average surfer feel as strongly ?
The average surfer probably would not feel as strongly. The average surfer is correspondingly unlikely to install plugins for Firefox.