[RobertoG]

Are we sure they will be collecting data?

You could get personalize advertisements without collecting the data: the browser has your history, it made some kind of profiling (categorize you), and then it request advertisement for your profile.

[rfk]

Indeed, the whole point of this (and all the verbiage about "respecting user privacy") is that the browser will do the analysis locally without sending history data back to Mozilla.