Actor and director Clint Eastwood's embarrassing 12-minute speech to the Republican Party convention, which nominated Mitt Romney as the party's candidate in next November's presidential election, highlights the perils of celebrity endorsements.
When everything goes according to plan they can provide the politician or product concerned with a useful popularity boost, but when things go wrong they can go very wrong indeed.
That was the lesson several major companies who had paid expensively to have their products and services endorsed by Tiger Woods learned the hard way when embarrassing details of the golfer's priapic excesses became public knowledge in late 2009. AT&T, Accenture, Gillette and Tag Heuer were among the brands that saw the value of their investment disappear overnight.
They were not alone. Eighteen years after he was first charged with the murder of his ex-wife, car-rental company Hertz has yet to live down its use of OJ Simpson to peddle its wares.
On this side of the Atlantic, Chanel and Burberry were among the brands to suffer embarrassment when a newspaper published pictures of model Kate Moss apparently sniffing lines of cocaine in 2005.
But our favourite celebrity endorsement gone wrong remains that of James Garner, the star of the 1970s' TV series the 'Rockford Files', who in the late 1980s fronted an advertising campaign extolling the virtues of American beef. The campaign had to be suddenly pulled when Garner was rushed to hospital for an emergency quadruple heart by-pass operation. Happily Garner, a Democrat incidentally, is still with us 24 years later, but clearly the perils of celebrity endorsements are still not fully appreciated.