Since we're all totally guessing here, I feel like I should point out that we're talking about FB scale here. Negligible minority for FB would be many products entire user count.
Well, it's only negligible within context. Nothing is just automatically negligible at scale but within the context of active users for a single day, I agree, it's negligible.
Assume the average such company has around 100 employees with 15 fake accounts each, now assume there are 1,000 such companies: that's 1.5 million fake accounts. At this scale, that is "a negligible minority" ;)
Presumably they only had 15 fake accounts because they put a lot of work into each account. If some company just optimized for quantity over quality, they could get that number up a lot. And if another company used bots instead of employees, they could easily have tens of millions of fake accounts.
No one pays me and I had over 20 FB accounts just to play games. A lot of games give you in-game rewards for referring your friends and allow friends to gift each other in-game items.
Edit: And most of my friends have two or three real FB accounts, one for close friends, one for older relatives/their parents' friends, and one for work acquaintances/bosses. I am in the minority in only maintaining one real account.
So that is 150 in the company. Lets assume there were 100 companies like this, each one 10 times bigger than this smaller company. I'm guessing that is actually overstating the reality. That is 150,000 fake accounts. That would account for about one percent of one percent of these billion logins. So very negligible.
Beside creating false rumours for PR objectives, another use of the accounts was try to reach 5000 people in them (I dunno now, but when she was my GF facebook converted people accounts with 5000 friends into pages with 5000 followers, then ad companies could sell those to kickstart company pages).
I would like to know more about this. Who is paying for fake activities, and to what ends?
Obvious guesses (with prior evidence!) is: Government astroturfing & information gathering (hot girl friends you + gov't gains access to your "private" content), and brand astroturfing.
Her fake accounts had as one of the objectives reach 5000 friends (when this happened you could convert it to a page with 5000 followers and sell it to a company).
To do this they created a program that searched the internet for pictures of someone in various situations, then prepared a easy-to-use library of photos to be uploaded every "x" period to look like a real person.
The account operator (or operators for some particularly prized accounts) would then log-in, post the photo scheduled, and write a post on the fly, the best operators could make the fake account look like a real person, fooling not only other users but bots, tracking software and whatnot.
The accounts that looked particularly real were very useful for PR efforts, some of the biggest clients were appliances manufacturers (example of one of them: GE), and one of the uses was for example one day try to distract the public after some bad news about washing machines causing accidents went viral, or try to create a counter-post that is viral too (in the washing machine case it worked, the viral post stopped being viral in 3 or 4 hours, and not even me remember what was the issue with the washing machines).
Absolutely mind blowing.