Generally people who dumpster dive are referred to as bums. That is unless you are a hipster then dumpster diving is a lifestyle called freeganism and the persons adhering to freeganism are called freegans.
The freegans not only dumpster dive but they also poke around on the streets looking for free stuff such as discarded furniture. Supposedly freegans do not want to be apart of the consumerism that is part of American life. Some also claim to be concerned about so many items, food or otherwise, going to waste. Also it should be noted that most freegans are not poor.
So these freegans dive in a few dumpsters, cop some free furniture off the street and they call it a new lifestyle. I'm sure however that actual poor people would beg to differ. Dumpster diving is a way of surviving for many people in this country and around the world and has been around for as long as there has been trash.
So this freegan stuff is not new and it's not hip. It's just another case of hipsters being clueless. If these hipsters really were concerned about waste they would stop wasting their time pretending they invented a lifestyle.