Linden Lab just announced a date certain scheduled phase out of Magic Boxes starting April 3, 2013. For those that don't know, Magic Boxes are holdovers from XStreet SL / SL Exchange and used by merchants to deliver products in-world from off-world Second Life Marketplace purchases. Each Magic Box holds copies of the inventory items being sold and they must be rezzed somewhere in-world in order to work.
Most merchants have already converted to Direct Delivery which puts purchases directly into the buyer's Received Items folder without the need for a rezzed box. However, a lot have not. The new policy gradually removes Magic Box capability over a two week period ending on April 16. After that, anything relying on a Magic Box will be delisted from the Market Place.
For full details, read the official announcement: Magic Box Retirement