the problem with time machine is that is backs up as a .sparsebundle, for security. sparsebundles save data in stripes instead of one big block, so in case of corruption you hopefully dont lose it all. But this is a brand new tech, and it is only supported on HFS+ drives in Leopard. So, not on an iDisk. yet? Apple being apple, i dont think they would want to step backwards to offer another backup solution, even if it was wanted/needed.