The aliens who show up in Rudy Rucker's Freeware offer humanity devices that can make pretty much anything, including more such devices, and it doesn't occur to them that this might lead to problems. It's only due to some last-minute persuasion that they don't hit the market, as it were, fully capable of whomping up a tonne of plutonium. The aliens apparently come from a part or period of the universe where the nature of time is very different, and the occasional yottatonne nuclear explosion is (while certainly unfortunate) not a catastrophe.