Its not just the addon bar, and its not just firefox. Its a wider problem, not just with open source or free software.
If a business model is predicated on giving free stuff to the public, the staff, directors and investors do not understand that its users or members have a legitimate ownership stake.
That they did not pay for the product or service, that they agreed to the terms of service or copyright license or even copyright assignment is not a consideration. That something is legal doesnt particularly imply that it is ethical.
Or that it makes sense. Look at the smoking radioactive crater that reddit the company made of reddit the website. I dont blame Ellen Pao, the problems arose long before she hired on. I blame the directors, the directors hired Pao to act as a spokeswoman for the ignorant.
The seo add on that didnt work has over one million installs yet firefox totally borked it.