Comment 16 for bug 147230

Wheel-based switching should be disabled by default. Most new users will move the mouse out of their way when browsing the web, but when they start to scroll down the page, they switch workspaces instead. It's a very disconcerting behavior and they won't know where their work/windows went.

If it's not disabled outright, then perhaps it should be changed so that the scrolling only works when a window is not selected and the mouse is hovering over the desktop. That way, people can still use the behavior if they want, but it won't scroll workspaces if the person is trying to scroll down in a selected browser window.