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It's all fun and good until someone tweets the wrong thing.

When the Olympics start Friday, social media is likely to light up with pride for sports, countries and various teams as they come together in Rio to compete for the next few weeks. But your local plumber will have to sit it out.

Businesses have long been expected to keep their Olympic excitement to a minimum, as they can't use the famous five rings or other symbols and phrases from the games, since they're all trademarked. The concern is that the organizations around the Olympics don't want corporate sponsorships to lose value -- imagine the horror if people watching the 100m sprint started thinking about Pepsi instead of a Coke.

But this Olympics is happening at a time when a billion people are using Facebook on their mobile device every day. Social media has become so pervasive that when you add in Snapchat and Twitter, the combined populations of people using these services is larger than any country on Earth.

So of course, in addition to the rules you can't use the Olympics' trademarked words or phrases, AdWeek notes businesses also can't use certain hashtags, including #TeamUSA or #Rio2016.

Never mind Twitter can barely keep people from sending the racist and misogynist messages to the female stars of the latest Ghostbusters movie. Now it'll have to police Olympic hashtags too.

Facebook, Twitter and the Olympic organizers didn't respond to requests for comment.

"Experts' advice to non-sponsor businesses? Tweet very carefully," AdWeek writes.

No kidding.