Dumpster diving involves searching through a dumpster for working but discarded computer equipment. Cash-strapped computer enthusiasts have been known to do this, as many companies throw out equipment that is in working condition but has been replaced by more capable models.
Largo is often seen in Megatokyo dumpster-diving, whether by accident or on purpose. When intentional, his motivation seems to be to get tech for his computer because, as he says in 211, "Companies are always throwing away perfectly good equipment."
It is currently up for debate whether the person to fall into the dumpster in 725 was Largo, however, it seems likely, given his drunken state and the fact that neither Piro or Kimiko are usually the butt of Megatokyo's slapstick humour.