If a petrol commissioner can't deliver lower fuel prices, what will the inquiry into grocery prices bring?

The Rudd Government's brief look into fuel prices led to the creation of a petrol commissioner and adoption of the Fuel Watch policy.
While being able to go online to find the cheapest at bowser petrol price nearest to you may go a small way to allowing consumer choice, it does nothing to actually bring costs down for an
extended period of time in what is supposedly a competitive market.
National implementation of this monitoring scheme may be difficult to achieve, and once the novelty wears off voter dissatisfaction is bound to resurface.

So what hope does Rudd's inquiry into grocery prices have when the ACCC's Graeme Samuel confesses himself at a loss to find any competitive edge between Coles, Woolworths and Metcash.
Although it has to be said that the degree of investigative fervour does not appear to be high, given that quite a bit of information received appears to be based on submissions and industry response seems almost casual to the outside observer.
There has been very little to show of Samuel's statement;
"We have the power to subpoena documents from parties who can assist us with inquiry, to subpoena witnesses to appear before us, because we will be conducting public hearings around Australia to obtain evidence from witnesses, that evidence will be given under oath.For the most part, it will be public, but in some cases, it may need to be confidential. So we have very, very extensive powers."
I'm afraid the National Farmers Federation may have hit the nail on the head when it called this inquiry a toothless tiger.

Kevin Rudd's early penchant for calling inquiries may quickly come back and bite his rear, if solid recommendations leading to realistic solutions are not forthcoming.
I very much fear that the result of the grocery inquiry will be an exhortation a la Wayne Swan for people to "shop around".