It is a step in the right direction but still not exactly a well thought out idea. Most of the people i know wouldn't use them for the simple reason that the reason they take the drugs in is to get loaded, they take the gear with them knowing full well there will be dogs & either risk trying to get through or dump before they go in and if i had just spent half a weeks pay on gear odds are i damn well wouldn't be throwing it in no amnesty bin so a pig can have a night out on me after they pocket it, I'd rather stash it and come back for it later. I reckon odds are there would be a sneaky fucking copper watching out for anyone making a b-line for the bin as well, anything for a bust!
I do however support it for the simple fact that it is a step in the right direction.
And also because it take responsibility away from the organizers and makes it a whole lot harder for the government to try and intervene and shut these places down.
Want harm reduction? Get rid of the dogs all together, it will save lives, or decriminalization of MDMA and related substances and have them produced in safe, government controlled labs. It's a win - win situation, we get munted and they get more of our tax dollars to give themselves end of year million dollar bonuses.