I have the exact same feeling of dumpster diving as adblock plus.
You do it? It's not 100% right, but you are free to do it. Just... don't start spreading this, or you will soon have a lot of people just waiting at the dumpster for goods instead of just buy them. It may put a huge problem in some businesses, especially those who are gone bankrupt and are trying to sell everything before shutting down. They will start destroying the stuff instead of throwing it away untouched and you will all be screwed over because you couldn't stop bragging about it.
Also, the business near my house has dropped something like 30 CRT TVs on the street. They were stacked and took a little space between my house and the office. Four hours later, stupid gypsies/poor people made a mess by spreading the small space designed to dumpster to a dumpster itself, even breaking some of the TVs, or taking their own trash. If you are going to take stuff from the dumpster then please, at least have the decency of keeping the space clean like it was before.