Browsing through the oldhouseweb.com BBS (as you may remember a hobby of mine) I stumbled over the following quote (in reply to a lady complaining about blue sparks inside the main breaker when turning on the breaker for the boiler).
>2)A short. A normal fuse or circuit breaker will NOT help you with this. A special GFCI breaker can, however.
What are CBs intended to do then?
At least he stated that he wasn't an electrician.

It's sobering to think that many people rely upon such advice, believing that those handing it out know their subject.