The "danger" in this case is a reduction in scarcity which would lead to all sorts of alternative uses for whatever they decide to tow back to Earth. If they p

The "danger" in this case is a reduction in scarcity which would lead to all sorts of alternative uses for whatever they decide to tow back to Earth. If they perfected a way to cheaply process titanium tomorrow it would suck for people betting on the scarcity of titanium but would be a boon for countless other uses of it that simply aren't economic today like stronger, lighter engine blocks for the family car. Admittedly I didn't read the wikipedia page so... --edit-- Ok, read the page and "nothing to see here, move along..." since no modern currency is backed by precious metals.