Social media just took a big left turn. Facebook now does hashtags. If you aren’t Twitter literate, a hashtag is what the ancient Mayans called a pound sign – #. But several years ago a bright young web guy – Chris Messina –  started the idea that a word or phrase following a hashtag could be a type of topical hyperlink. The concept caught on and Twitter users began hashtagging everything. That led to trending topics and became a means to see what the twitterverse thought was the most important or at least most popularly discussed idea of the moment. There are humble hashtags in use on Flickr, Instagram, Tumblr, Google+ and probably it’s coming to every social media platform there is.

Now the hashtag phenomenon on Facebook. In my opinion – it’s gonna get messy. Facebook says it isn’t “selling” hashtags to brands and advertisers, but is encouraging marketers to use them. There’s a double-edged sword. Let’s say you’re a fine Texas brewery and start tagging all your advertising with the hash #Shiner. That’s great. But you have no control over that tag or who puts what into the conversation. Suddenly your post about the wonders of Shiner as the nectar of the Hill Country is inserted in between a frat boy who got hammered on #Shiner last night (complete with his buddy’s photos) and a protest by MADD against drive-through beer barns selling #Shiner.

On Twitter that’s not a huge problem – Twitter is fleeting. 140 characters and it screams through people’s feed like beer through that frat boy. But Facebook lasts a little longer. Things are more permanent. They remain on your timeline forever, or until Facebook reworks it’s platform and changes everything, so technically ‘ever’ could only be 18 months. Still, that barfing fratboy could still be linked to the #Shiner hashtag on their Facebook page for a long, long time.

Time will tell how hashtags change Facebook. Some don’t think it will be a big deal. I personally think it’ll be as big for Facebook as it was for Twitter. And I can’t even remember what Twitter looked like before the hashtag.