Forcefully installing ads, or enabling plugins is a big no-no, and a company like Mozilla should be aware of the implications of its actions.

While advertising is a given in todays day and age, when it comes to the authority or actions of software, ultimately the user should be able to decide. 

It is perhaps why programmes like little snitch are becoming more popular as a way to alert users when applications are performing unusual tasks, or sending data to unknown locations.