Do citation counts explode like news in social networks and when did this start?
This seems like a naive view of citations. They aren't "likes" or even recommendations to read a paper. They reference things that actually support and form a background for a new work. 

So, if citations suddenly explode within a field, and people are working honestly and not just gaming the system, then that field must be pretty hot with a lot of actual research going on. 

And gaming the system outside a small working community is pretty hard since a lot of people need to cooperate. 

But some fields are indeed hot for a while, with a lot of research, hence citations. But then they cool. Some future discovery may heat them up again and the cycle repeats. An a fresh discovery can often lead to new ways of looking at a problem and that, alone, will generate new ideas and new papers and new citations. 

But a small citation count doesn't necessarily mean that a paper is unimportant. It may be incredibly important, but only to a small set of researchers. On the other hand, a less seminal paper might have a high count if it appears in a popular field. 

And a there are a lot of people who aren't drawn to popular fields, thinking they will be just a face in the mob. 

But research in general is hard. Facebook requires little actual intellectual effort. A paper in Nature requires quite a lot. 

“If we knew what it was we were doing, it would not be called research, would it?” ~~Albert Einstein