Thats actually a pretty common thing over on the AussieHomeBrewer forums.
Usually someone starts a thread stating their intent, then a whole pile of people reply to say they're in, sometimes stating that it's price dependant.
Then when rough numbers are known, the OP starts contacting suppliers for best deals, mentioning which competitor can do what for him.
Then when the best price is found the OP replies to the thread with details, and everyone replies if they're in or not.
Payments are usually made direct to supplier, then shipment is made to ONE pickup point in each major city.
People that are slow to pay or pull-out/dissapear are named-and-shamed in the thread... no excuses.
I've been involved in a couple of bulk buys and they went well, without a hitch.
My most recent was for a couple of kegs, got them for around 30 or 40% off retail incl. freight
