clubbing together
How about *.sucks, a TLD devoted to customer complaints against big brands.
The rules of the registry are that trademark owners *cannot* buy their own brand names, which in turn means that anyone going to (for example) www.theregister.sucks can be in no doubt that it isn't affiliated in any way with the well-known brand. Thus, the usual "passing off" argument that brands use to silence their internet critics is whisked out from underneath them.