It got really bad. Initially when Brawl was first unveiled, over half of the suggestions I saw were for third-party characters. Heck, there was even a significant minority that believed that we would receive more third-party characters than Nintendo newcomers. Sakurai quickly squashed that when he said that there would only be one or two more third-party characters after Snake.
However, even after the third-party character thing wore off things still got pretty bad due to a misinterpretation of Sakurai's various statements. For example, people misinterpreted Sakurai's reasoning for adding Zero Suit Samus (that Smash had few female characters so it was good to add another female newcomer) as him saying/meaning that he would go out of his way to add female newcomers.
There was also a lot of people who liberally applied Sakurai's statement of "there will be cuts". You had people saying that Dr. Mario, Pichu, Young Link, Roy, Falco, Mewtwo, Marth, Mr. Game & Watch, Ice Climbers, Sheik, Ness, and Jigglypuff would be cut.
There was also basically a lot of character cults running around as well. The Ashley fanbase literally exploded out of nowhere simply due to the "Ashley's song" Dojo update. In general character fanbases were extremely fanboyish and scary, particularly the ones that were among the less likely to get in. It was horrible.
I can't really think of a really fanboyism fanbase this time around. There is enthusiastic support for Ridley, Mewtwo, Mega Man, and K. Rool, but aside from those four its pretty much it (probably Waluigi as well). Little Mac, Isaac, Palutena, and Roy are among the most wanted characters this time around, yet don't really have loud supporters.
However, I am thinking we will probably see a return to craziness once Smash 4 is formally unveiled.