I too find that would be a good idea - that way the owner would know it had been picked by somebody and wouldn't continue to pour items into it thinking it was still locked, only for the picker to have continuous access.
Also, Godfrey, that's an interesting premise, but unless the server can host spout completely plugin based (not possible as far as I know, feel free to correct me) that would limit the server to spout users.
I know spout can be installed on all computers, but on some it may not run as well/and or properly at all. As well, many players (including myself) would need an exact walkthrough on how to install it properly on their platform. I don't think anybody wants to do that even once.