Frightening for others, it threatened to shake the fragile frame of treaties and understandings that prevents a new nuclear arms race. If you listen to the talk of the Bush people during the campaign, this thing is already way out of control. Robert Hunter was US ambassador to NATO for five years under the Clinton Administration. It backed off National Missile Defence or NMD last year, when two more tests ended in failure, suggesting the technology wasn't ready. And as for putting things in space, I mean, that's way off in the distant future.
Space is probably doable, but farther out in time - a decade or more away.
But many, like military analyst Daniel Goure, insist NMD from land, even ship-based missiles, is all but developed now. There's a great deal of background in this - it's not really science any longer. Almost all of it is a matter of engineering and money. It may not be the best warhead, it may not be a nuclear warhead, but it can do it already. With that concern, George W. Bush campaigned for president on a promise not simply of resurrecting Bill Clinton's modest land-based missile defence plan, but pushing much further.