The company denies this. They claim that they the reason the new feature was added was to help fund the further development and optimization of the browser. Mozilla also stresses that no new data is collected, stored, or shared with the companies on the recommend list or anyone else.
There are a few additional pieces of information to be aware of:
It all sounds rather innocuous. At the end of the day Mozilla has decided to display ads. No matter how careful the vetting the list is pay to play. No other major browser on the market today has to resort to such trickery to fund further browser development.
Thus far users have taken a dim view of the addition and it's hard to see how the company can turn that around. They don't have an impressive market share as it is and this will certainly drive at least some from the fold. Unless Mozilla has something truly incredible in terms of upcoming features there's not really any compelling reason to go back to Firefox once you leave.
If you use Firefox and you're frustrated by the new feature either disable it per the instructions above or give some serious consideration to finding a different browser.