While doing some research on using SuperDuper as an alternative to the not-yet-Tiger-compatible Carbon Copy Cloner, I stumbled across this warning from the authors of SuperDuper. Despite the warning being a week old, I haven't seen any mention of this anywhere else. This lack of publicity would be unusual for what should be a major Apple news story so it may be that this is a false alarm, however it's always better to be safe than sorry. The essence of the bug is that mounting sparse disk images over 1GB in size will corrupt the image, destroying all data in it.