Direct Delivery is rumored to be on the verge of release. So, Darrius’ article may seem a bit untimely. However, until Direct Delivery (DD) actually arrives, the information he provides could save you lots of headaches.
Check out the article at his blog: Care and Feeding of the SL Marketplace Magic Box.
This is the most complete information I’ve come across on Magic Boxes. If you are having a problem with one of your Magic Boxes, the solution is probably in the article.