I personally don’t find those kinds of videos funny, same with people who bomb on talent shows (Idol, X factor, Various country’s got talent).
When its people genuinely trying to perform, and people laugh at their incompetence, lack of skill, awkward, or nervous behavior I find it to be cruel.
When its a comic act (Tim and Eric do this type of humor allot) doing it intentionally I find it annoying and lacking of substance.