I think ECMA-262-5 7.9 pretty concisely sums it up... and at the same time there are plenty of nasty examples in the "FUD" section at the bottom of the article.

I think ECMA-262-5 7.9 pretty concisely sums it up... and at the same time there are plenty of nasty examples in the "FUD" section at the bottom of the article. The spec very clearly says they may be used, so I trust no one will have a problem with me using them. It's tough to drop that old C habit, anyway. Even my Python code has a random scattering of semicolons at the ends of lines.