I have thought about this today. My thoughts were that it would be neat if any product or service could be purchased as a "group deal". Example.

I am selling snowboards at http://illuminatisnowboards.com ;). It would be cool if my customer could choose a product attribute of "start group purchase" (maybe even multiple options i.e. group of 5, 10, 20 as pre-determined by admin). Choosing this option would "Activate" a current group purchase of the chosen qty.  The pricing deal would only go active if that particular group gets to the pre-determined amount.

So, the customer would see an attribute option like:

Purchasing Options:

- 1 for $299.00

- 5 for $249.00 each

- 10 for 199.00 each

- 20 for 179.00 each

If the customer adds it to cart choosing one of the group options, it either 1. starts a new deal if no deal is active for that product. 2. Prompts to join an existing deal 3. Offers the single price option for full price

There could be a flag (cck field?) that shows up of a particular product is associated to any current group deals.

For example; I am browsing for a snowboard and I notice the one I am looking at has a flag on it that says something like "Group Deal Active" (click for more details) On click, a pop up could display the details of the deal, and the status, and an option to buy"

Thats my two cents for now.