In a word "Fanboys" ... It is actually worse that just being a fanboy flame war though
Back in the day it was generally accepted that Sega fanboys were typically the most laid back largely because they stoped focusing on wide spread success largely because Sega could never become successful; in a lot of ways Nintendo fanboys have followed in the same path after the N64 and Gamecube were not all that popular.
Sony fans are not used to things not going their way and every time something good happens for the Wii (or something bad happens to the PS3 or PSP) they throw a tantrum.
Trust me, on Thursday (after the Japaneese weekly and American Monthly charts are published) you will see every sony fan do everything in their power to bash the Wii ...