reference of "this"

Is the highlighted "this" referring to "It is, in short, a force for good" or "Mobile clubbing"? How to you understand it?

Context:

Mobile clubbing is an offshoot of flash-mobbing, a fad that was predicated on its ingenious pointlessness. The point of mobile clubbing is that an activity normally reserved for special occasions and places – parties, nightclubs – infiltrates daily life so thoroughly as to be indistinguishable from it. It has the guerrilla quality of illegal raves but is totally legal. It is, in short, a force for good. This has become more pronounced since the London bombings last year. Stations are prime terrorist targets. You are going about your business and, in an instant – boom! – everything is changed terribly and irreparably.