Keeping processing history in headers

I too think it is great. Having a track of what was done to the file before it came into my hands is highly useful. Even if nothing was done to it other than conversion from SEG-Y, that's still a piece of information too. When the file is not raw data but something more downstream, i.e. velocity model or migration result, knowing how exactely the data was processed before me (and when, and by whom!) is invaluable.