This is something I've noticed for a long time. Many communities have this occurrence.

usenet, 4chan, reddit, world of warcraft, the "internet" itself etc.

Any networked service can fall victim to this pattern. The original community can quickly get displaced and drown in the wake of rushing users and the powers that be will respond to the will of the majority thus betraying it's original intent.

Not all fall to this, but many do.