I caught this article from Nature (Satellite kill creates space hazard) about a recent mission by the Chinese space agency to destroy one of its own defunct satellites in order to test anti-satellite missile technology. While they were able to destroy the satellite, scientists worry the shrapnel generated from the blast could pose a dangerous threat for other orbiting objects, including their own functional satellites.
I think the people at NASA and the Chinese equivalent have been watching too much Star Trek. The solution is pretty easy. Why not just incapacitate it by pointing it in the wrong direction, hijack it, or, even better, use a "soft" modality like insta-foam to render it useless? Like the article says, all you need is a basic guidance system with a digital camera. When the missile comes close, it shoots out its foam which covers the satellite of choice and then solidifies. Kind of like a cosmic foam party (see right). Sounds too low-tech? Just, check out the Mars Landers and their airbags they used to "crash" onto the surface of the Red Planet.