Dogpiling at the conclusion of a championship sporting event like the World Series is such a positive, celebratory event. All those people rejoicing happily in their hard-earned, if sweaty, victory are inspirational and moving in their unity and joy.
This makes me wonder why the Internet's version of dogpiling is less about spreading the love and more about making people wonder why they go online in the first place. Online dogpiling typically occurs when a person says something that others don't agree with (are you starting to notice a pattern, here?), and the comment thread is then bombarded by a mob of rabid dissidents who unleash a torrent of insults designed to make you take back your opinion and/or scare you off completely. GamerGate again demonstrated how dogpiling could make a Twitter account unusable by bombarding it with negative messages.
Of course, the mob mentality is nothing new, as anyone who has ever read "Lord of the Flies," or has gone to one of those pop-up discount bridal shops knows. It's just another sad example of the anonymity of the Internet giving people a heightened level of bravery previously supplied only by large quantities of alcohol.