But where would be the benefit for them? How many people would pay to block adverts but not tracking & data linking forensics when they can already do that for free? Probably some would, but I suspect not enough to offset the extra development & maintenance time and potential sense of bad faith from the advertisers. Further more, as mentioned in my previous post, making an official ad-free route is likely to make unofficial blocking easier.

Who the advertisers might want to reach is relevant because FB can currently promise to do whatever is practically possible to block ad blocking. This doesn't amount to much (tricks like the extra divs littered through the word "sponsored" and so forth, to obfuscate the advert related code & markup from blocking scripts, for instance) but is better from the advertisers point of view than them admitting it is going to happen and they've given up stopping it. And again, the official ad blocking method is likely to make unofficial blocking easier - they would have to defend that to their advertising customers.

The other issue that could come up is effectively creating a two tier system, with those that can afford to pay and those that can't. Equality and privacy defenders might be all over that, and however right or wrong people think each side would be there FB are not going to want that on top of all the public scrutiny they are already getting.