Adding a leading semicolon just in case seems like overly defensive programming to me. You ought to pick trustworthy tools. If your script concatenator doesn't work right, I think it's better to fail fast rather than let things quietly be half-broken all over the place.

The preceding semi-colon is definitely a very smart advice. I also will have to try out jshint (I've been using jslint).

It doesn't even need to be a semicolon. It's also common to see a ! used for this purpose.