I have even apprenticed under a master and given lessons in various cities.
Over the last 20 years I have found all sorts of things in the trash including 100+year old scotch, Scrap silver, working computers, Herman Miller furniture, 1000's of Camel bucks all together, the list goes on and on....
There is a case from the 80's that is often referred to in cases of dumpster diving.
California VS. Greenwood is the case. here is the link.
http://en.wikipedia.org/wiki/California_v._Greenwood I carry a copy of this decision in my back pocket as part of standard equipment.
Also every dumpster diver has to have a set of careful ethics. There are things like don't leave a mess, be quiet, don't take more than you need or can give away, erase the data on all computer products, and most importantly leave the information diving to the politicians, (Nixon employed fulltime divers to get dirt on opponents and garbology was actually started by the intellegence services).
Personally i don't gleen food products. This is not due to the food being unsafe. It is a matter that a tomato is not worth my time if I get harrassed by some cops with only a slight familiarity with the law. It seems that in this case even the DA didn't know what the law was. But i also have to fault the divers.
For all their trouble and trying to get free food they easily could have found some old chair, sold it to a local junk shop, and been able to eat organic produce for a week. It looks like they saw the Freegan video instead of visiting a site for divers that aren't afraid of using barter to get above the hunt/gather stage.
For anyone who wants a good site for this try
http://www.dumpsterworld.com/