Google often uses an undo system where an action is followed by a popup asking if you want to undo the latest action.
This is probably satisfying for the most of us - but how often do people regret the second last thing they did, and thus with this system, can't undo that? Are there any studies on how satisfied people are with this kind of design?
I like the system but I really feel that it is a potential problem since you only can undo the last step.