Bombing doesn't have to take place on stage during a live comedy show, it can happen when one comedian tries to improv with another, far more talented comic who just naturally shows them up.
It used to happen all the time on live broadcasts, and those YouTubin' youngsters of today don't know how to be spontaneously funny instead of formulated and rehearsed so they tend to clam up when the live cameras start rolling.
Watch as PewDiePie, a supposed comedian and "video game megastar" who has millions of subscribers on YouTube for some reason, gets shown up by the naturally funny Conan O'Brien.
Oh, and they play Far Cry Primal too! (Barely NSFW due to language)
To be fair, young PewDiePie was probably transfixed by Conan's amazing pompadour, I've heard it can be quite distracting when seen in person...
-Via FAIL Blog