Wide tire on narrow rim.....need thoughts, please

On a message board I frequent, there is a heated discussion going on about the dangers (or lack thereof) of mounting a wide tire on a narrow rim.  Specifically - we're talking about taking a rim designed for a 160 - max 170 and fitting a 180 or larger.

Most can agree that the contact patch, sidewall and profile is adversely affected.  However - a few of us can recall a report that a rider was killed last year when his 180-fitted-to-a-narrow-rim blew off the bead, causing him to suffer a fatal crash.

None can seem to verify this potential Urban Legend.  So....

Is it a real possibility that fitting a wide tire on a rim not designed to accept it may result in the tire coming off the rim?  We all know "it is possible".....is it a real problem - or is it more legend?

Thanks.