Actually I think it would be useful if the forum software would enable that automatically upon account creation, although that could lead to ballooning disk space.
If you made it the default, you'd need to set up a system which alerted users when their PM box was getting close to the limit. Someone's inbox being constantly full is more annoying than them not having PMs enabled and it leads to a shitload of "empty your inbox" threads.
Well, I've used forums where there is a limit on the number of PMs, and frankly it is downright annoying. I'm not sure if there is a limit in the current system, but I haven't hit it and I keep all my communications.
If there was going to be a limit, I would like a way to export PMs to a .csv dump file, and possibly even have the export signed by the forum for safekeeping.
Also on a slightly off-topic-ish tangent, I also use a feature of the current software extensively - that of Labels. They can be used as folders by adding a label and then removing the inbox label. So for instance, you could set up labels for "processed" or "hardware sales", and then add one or more labels to a message. Once you remove the Inbox label, it disappears out of the Inbox, but remains accessible in the other label sections. Unfortunately, this can't be done with outgoing sent messages.
