Where one goes, others will follow...
This is especially true in WoW. How many times has it happened that one person is doing something, and another joins? And then another, and another, and another, all doing the same thing, until it's a huge mob of people?
As WoW players, we love to do it. We love to get in mass mobs of sameness and terrorize the countryside, or terrorize instances. I've witnessed the great Mammoth March, and though I was unable to participate on my diminutive Ram mount, I was able to run alongside, snapping photos. Horde and Alliance alike merged into a relatively single-file line, following the leader seamlessly, even as he went around corners and cut through the middle.
It can be started by something even so innocuous as sitting AFK. Two players, a tauren and a draenei, sat side-by-side on the edge of the landing, mounted on bronze drakes. I didn't have anything to do or any place to be, so I mounted up and say next to them. Then others would run up to us, mount up, and settle around the perimeter. One tauren, lacking a drake, mounted his netherray or danced in bear form. The blob morphed from short line to pyramid to long line, with drakes, protodrakes, wyverns, netherrays, flight forms and hippogryphs, though the majority were always bronze drakes.
Druids, however, are perhaps the most notorious of mobbers. Two druids dancing in a form will suddenly call into existence half the population of Dalaran to appear and dance along with them, forms changing and tranquilities going off, and double hurricanes adding atmosphere. What you aren't always aware of, however, is that we use these groups to discuss current, on-going and troubling issues, as well as to prey upon other classes.
Can you pick out the Horde druids?