SSB was SO bad online, people still try to play that???
Tatsunoko/Brawl are subject to tons of lag/delay.
Project M. People play that mod on WiFi, believe it or not. Of course, it's only via friend code exchanging (since random WiFi would just desync) but it's still being used for something significant. This really will affect that community of players now. It'll even affect the AiB ladders (AllisBrawl) hugely, which is what the site was founded on. Its main purpose will be gone until Smash 4 comes out. Truly amazing.
This is a real surprise coming from Nintendo, it really seemed like they would never cut out the servers for any of their games. Absolutely crazy that everything, even released within the last two-three years (Pokemon White, White 2, Black, Black 2 for example) are affected and closing up shop. I guess that's what happens when you release a title so late into a handheld/console's life cycle now, huh? Its online functionality is likely not to last more than 2 years. =\