You've all heard it before: when you transmit a signal into a receiver from which the original signal originated and the signal gets retransmitted - over and over again. If the original signal gets re-broadcasted at exactly the same amplitude, you hear an echo. If the original signal is dampened, the signal echos, but fades with each cycle. If the signal is amplified, you can create all kinds of problems (blown speakers, for example).
There is a special type of feedback; one in which the original signal matches the harmonic frequency of the transmitter. The result is a harmonic oscillation. The linked example is the result of 25 mph wind that caused the Tacoma bridge to swing back and forth at its harmonic frequency. Its also important to realize that the bridge regularly withstood much higher wind speeds. Here is another example of a harmonic oscillation. In this case, the rotors of the helicopter are spinning at exactly the same harmonic frequency of the helicopter's body. Ironically, the rotors were spinning within the normal operating speed of the helicopter, so you can imagine how scary it is to throttle this vehicle through that specific range of rotor speed.
There is a social analogy to this phenomena. If one person, lets call him Hilmar, says something that provokes a response from another person, lets call him Pod Pilot. Pod Pilot's response matches Hilmar's harmonic oscillation and Hilmar's response matches Pod Pilot's harmonic oscillation, the system amplifies itself until the two participants annihilate each other. This doesn't even have to be a heated exchange. Even a small feedback loop can create a catastrophic event (bridges should be able to withstand a 25 mph wind).
I watched a small portion of Fanfest this morning. If CCP doesn't pay more attention to the unintended consequences of their game design, they'll find themselves in this destructive feedback loop. I'm not going to offer specifics because CCP didn't offer any specifics, but I'm starting to suspect that Incarna will be the first cycle in the feedback loop.