We recently had an admin accidentally change the wrong variable in a deployment because they were not paying attention. In this particular instance it was important since it was a connection string. Since variables with the same name appear on top of each other if they are scoped differently, he thought he was chose the variable for the incorrect environment. I understand this will be helped a bit with the new UI, but a variable "lock", something like a confirmation checkbox that you would then have check to "unlock" or some simple mechanism that would prevent someone from inadvertently changing and important variable. Obviously this is something that you would want to have the ability to apply to just specific important variables, and not all.