It's not legal for a consumer to pretend to represent a company if he doesn't. Does it make any sense for marketing executives to impersonate customers? In a way, that's what advertising has always done. Now that we're leveraging new tools to get company messages across, some of the rules are changing.
In his blog, Communities Dominate Brands, Alan Moore talks about a new law in Europe that will penalize companies that use New Media tools to pretend to be their customers.
In America, we've already seen some high profile blunders caused by companies and public relations firms that thought they could sneak a company spokesperson into a blog or podcast without telling their audience.
It's one thing to put a smiling face in an advertisement and hope that people jump to the conclusion that they'll be smiling too if they only buy the company's product. Don't try that with a blog or podcast. The results will not be satisfying.