I don't know, Rommel used tanks effectively in N. Africa, that's pretty wide open.
Look at year... And think what changed in anti-tank weapons since...
Without air superiority, tanks for defense will be worthless (See Iraq circa Jan 1991, or more recently, Georgia, Aug 2008).
Concerning georgia - quite a number of georgian armoured vehicles that was taken by russian army was simply abandoned by crew, fueled and loaded with ammo. So, there was not so much entusiasm on georgian soldiers side to fight and die for Saakashvili stupidity. Not very good example here.