Chat is limited to 'marcos' so they can't actually spam abuse. You can see it in use on the video Blam posted.

And the inability to quit is common with 99% of online Wii games. When online the Wii disables the ability to switch off/standby, it turns off the home button (so you can't quickly drop to the menu) and unless the programmers go out of their way to add an option to leave mid game (some FPS have it, but no others do) then the only way to leave is to cut the power to the console.

Basically the only way someone can be a tool about it is when you're playing in the same physical room as them, and well that's part of the fun. ^_^

Oh, and for people who either haven't paid attention to the info & vids or have been living under a rock - when you are having to wait for someone to play online you get to mess about in SP, so you're not staring at the screen.