- What if most of your users come with an empty cache?
- Do you considered that with an extern .js file, a request will be made to this file at every page request, if the website is not configured properly (and usually, it's not),
- Is .js file really cached (with IIS, it may not be so easy)?
- It may be bad.
- Or it may not mean anything at all.
so rather shame on the person who says "very cool site, shame about the inline scripting in the source code" by looking just at the source sent to the browser, without knowing anything about how the website was done.