You're talking about kb's of data.. Not megabytes. Shallow argument.
I'm not giving an argument in any direction, I'm just adding on a comment from a user who seems to be assuming that once wifi is connected there's no mobile data.
For some users without 3G signal that is actually an issue. If you only have EDGE signal, very often your phone will appear as if disconnected if you get a call, and that is because the phone is keeping the push connection alive.
I don't really care about a mobile data shortcut, I would only ever use it if I'm roaming abroad.