Re: It would seem obviously unwise to invent something that could eat away *any* matter you put near it for the sake of self-reproduction.

Like a bacterium that could digest *anything*? It would be a neat trick. What happens if it meets another creature of its own type?

Note that the behaviour of replicators is not terribly different from the way AIs tend to slurp up space/time and mass/energy and convert them into utility.