It goes without saying that Facebook probably regrets engaging Burson-Marsteller to conduct a whisper campaign against Google (especially Facebook's "adult supervisor" Sheryl Sandberg, yesterday's BusinessWeek cover story). And Burson probably regrets agreeing to do it. But what can agencies learn from this embarrassing episode? What impact will it have on the reputation of the PR industry? Tune in to hear a conversation between Sterling Communications VPs Jay Nichols and Kevin Pedraja.