The Facebook API has been useless since 2014 when most access to friend data was cutoff. Since then, if your objective was data collection, that could be easily achieved by scraping publicly available information (many friends lists are public, there are many public posts, etc. - certainly enough to use in aggregate to formulate campaign strategies etc.). I suspect that will be the next “scandal,” since in 2018, people can’t possibly take personal responsibility for the things they post and allow to be public.
Ironically, the “scandal” that caused this whole thing is a non-issue. Pre-2014 Facebook apps could collect a lot of information about you and your friends, along with their Facebook user IDs, and that was scary because there was a time when you could simply submit a list of user ID’s that you wanted to show a specific ad to. But since Facebook advertising cannot be targeted by user ID anymore, and this policy was in place well before the 2016 election, all of that data was essentially useless to any participant in the 2016 election other than for aggregate things like general campaign strategies. I am intimately familiar with the advertise by ID issue - I was awarded a $2k Facebook bug bounty for spotting an exploit in the Custom Audiences feature that allowed an equivalent version of targeting by ID after they disallowed it.
So while it’s possible that Obama used his special access to the entire US social graph to successfully influence his elections, it is impossible for Trump or Hillary to have done it even if they had the data because of the changes in the FB ad platform in between 2012 and 2016. This entire “scandal” was created and promoted by people that don’t understand, or actively ignored, this concept. If you ask everyone that has read the recent headlines, including reporters that wrote the stories, I’ll bet 99%+ will tell you that they believe they could be specifically targeted with ads.
It would be interesting to see if the executives at any of the media companies that have managed to sell this scandal to the public took unusually large short positions in Facebook stock before releasing the story. Since the story is effectively fraudulent (it was not possible for the election to have been influenced in the way that the stories imply), I assume that would be securities fraud.