Who doesn't like a nickname?

Just read an article in The Telegraph about how Chevrolet have sent out a company-wide memo asking staff in the US to stop referring to the brand as 'chevy.'

This seems a little odd to me. Surely, the fact that the company has a nickname means it is familiar to people and that can only be a good thing? Apparently the recent desire to lose the popular 'chevy' nickname stems from their new advertising agency who have claimed that it is bad for their brand. Said agency then went on to cite the success of big brands such as Apple and Coke...is it me or is Coke not a nickname for Coca Cola?! I for one still plan on calling Chevrolet 'Chevy' and they can't stop me!