It was bound to happen at some point, Nintendo recognised there could be some flying wiimotes during intense gaming and introduced the strap for the wiimote, it looks like they underestimated the power of the American population as reports of broken straps are already appearing over the internet.
As I type this third party manufacturers will probably be putting together their own lifetime guarantee versions of wii straps, but for the time being be careful with your wiimote, apparently it"s solid as a rock, but walls and TVs are not.
IGN posted a video about a wall that felt the power of the wii when a strap failed, and Kotaku has a picture of a TV that had a chip taken out of the screen, courtesy of the Wii.