When you don't turn on the C-Gear in the beginning of the game (B/W/B2/W2), it tells you that some features will be restricted. Exactly what restrictions are they?
well, basically, it means you cant use these things:
you also cant mess around with it and change stuff on it while it is off, such as customizing it.
One last thing, surveys cant be checked with the C-Gear off.