I'm on a few teams that have done this, and it seems to have been pretty successful. I think it's a great idea, especially if you're wanting to help bump up your number of sales! The idea is that two shops will buy items of equal value (including shipping) from each other. It essentially ends up being a trade. You both come out with positive results! Not only do you get something neat, but you also gave each other another sale to add to your numbers. You can also offer to do item/photo trades. One member can sell an item to another member in exchange for that member getting good photos of the item and sending the photos back.
If you are interested in doing trades, post your shop link here. Just be sure to also specify the following things:
1. Amount you're willing to trade.
2. What areas you're willing to trade to (US, United Kingdom, etc).
3. If you want photos done of your items.
4. If you're willing to do photos.