Currently if you purchase something in world via Caspervend there is nothing notating this purchase on the marketplace or vice versa. Connecting the two to so both are aware of what you've purchased before would have multiple benefits.
1) Reorders - You would not need to hunt down a store location for reorders. If a store does decide to eliminate their in world presence, you would still be able to request a reorder via marketplace.
2) Eliminating Duplicate Purchases - Some of us have a rather obscene inventory count. It can be rather easy to accidentally purchase something on the MP or in world that you've already purchased via the other system. Specially since names of items can be different on MP vs in world.
3) Reviews - If you purchase something in world you can't review it on the marketplace. This prohibits you from supporting your favorite stores on the MP or providing valid criticism.
4) Eliminate Duplicate Work - Currently store owners have to do double the work, listing both on the MP and in world. This can take a considerable amount of your time, which could instead be spent enjoying Second Life or creating even more products.