His aha moment came when he learnt from a social media savvy friend that one of his waiters was mocking customers on his Twitter account. The comments were probably meant only for friends but unprotected tweets can be seen by anyone and with enough retweets could easily reach one of his customers. They also didn't mention any names, but customers could easily recognize the incidents.
Whether it is a good idea to ignore social media is debatable, Social media refuseniks tend to underestimate the impact and social media evangelists underestimate the costs, so in some cases the return is less certain than you might think. But you really don't have any choice about the social media policy if you are an employer because your employees are likely to be active even if you aren't, so you need to have rules or at least guidelines. These rules can help reduce the chance of any negative incidents and also make it easier to discipline employees who have caused issues.
Fernando probably doesn't need a full-size corporate social media policy because his needs are so specific they can probably fit in a few bullet points, but for any more complex business you need to have a more formal policy, communicate it and enforce it. If you don't already have one there is no point creating one from scratch because you can find may examples and templates just by googling "social media policy template" which will lead you to useful sources is the site http://socialmediagovernance.com
Just having the policy might please your legal department, but it is not going to solve any other problems unless you communicate the content to employees in some understandable way. The ideal is to add this to a training program, but when there is no time or budget for that you should at least be presenting the rules in a simplified format that can be digested, understood and accepted. Most breaches of policy are unintentional and they can be stopped by a few bullet points, leaving the formal policy for those cases where you have to bring in the lawyers.
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