Today, 4-16-10, is Foursquare Day. Rejoice, Foursquare users! (Foursquarers? Foursquares? Foursies?) Finally, you have a day of celebration where you can attend parties filled with Foursquare users. And earn a special badge. Also, you can check in to places. And stuff.

If you’re neither a Foursquare user nor a social media news junkie, you probably have no idea what that means. In fact, to the non-koolaid-drinker, the idea of a Global Social Media Holiday is exactly the kind of self-indulgent narcissism that is “wrong” with Social Media. Can you do that? Can you just… declare a holiday? And then get thousands of people to celebrate it?

Yep. You can now. And for online communities it’s really, really smart.

According to the official Foursquare Day website, here’s how it started:

Nate [Bonilla-Warford] is amused by simple number relationships like squares and primes and he makes a big deal about Pi Day each year. The thought struck him that since four-squared equals 16, it would be great to check into Foursquare on the 4^th 16^th of the year, otherwise known as 4 / 16 or April 16^th.

Nate floated the idea on Foursquare’s Getsatisfaction.com forum on March 12, 36 days before April 16th. An entire week passed with no activity before Kenneth Glanton suggested a Foursquare Day badge. He shared the idea with many of his friends on Twitter. Prompted by Ken’s enthusiasm and the recent excitement over Foursquare’s success at SXSW, Nate wrote up the Foursquare Day proposal and started a Facebook event on March 22, with 25 days left.

Nate then joined forces with Laura Petrolino and Jessica Barnet, which led to the creation of a Facebook Fan Page, multiple blog posts, and an official Foursquare Day Twitter account.

The idea took off. Users are hosting over 150 events all over the world today. Users. Not Foursquare. The Foursquare users. Foursquare Day is grassroots community building at its finest.

This is different than a corporation hosting hundreds of mini events. With social media, average users now have the ability to coordinate a network of simultaneous events. An influential blogger will suggest an idea, that idea gets put in motion, and then hundreds of people around the country think “wow, that sounds fun” and duplicate it.

For another example, look at mommy bloggers. Mom’s Nite Out started in similar fashion, with influential blogger Maria Bailey suggesting a national “night off” for moms to get together and have fun.

From the official Mom’s Nite Out website:

The National Mom’s Nite Out is the first nationally organized celebration of motherhood Intended to bring together today’s moms, physically and virtually, The National Mom’s Nite Out will unite over 150 social media groups, companies, local playgroups, mommy bloggers and mother social networks in giving moms a well deserved night off.

It worked. Hundreds of events popped up around the country. Power members among the mommy blogger community took it upon themselves to host them. “Hey, is anything going on in New York City? No? Ok, I’ll host one!” This led to a trickle down effect as more bloggers and readers followed suit.

Live events have a dramatic effect on your online community. When your users are the ones empowered to host live events for like-minded people, it multiplies that effect exponentially. They create a positive feedback loop, not only by instilling a strong sense of camraderie, but also by exposing your community to non-members in a fun and interesting way. How many people who don’t watch football attend Super Bowl parties?

This is exactly the kind of emergent behavior that Foursquare needs to target in order to melt faces.

Viral live events have a profound impact on gaming communities, too. Just look at any video game that has a robust grassroots tournament scene. Almost always, these tournaments developed in the living rooms of average gamers. They invited others to play, who in turn invited others to play, and so on until suddenly you have 6-figure prizes and rockstar professional gamers.

The lesson: powerful viral growth happens offline.

The Chronicle of Higher Education has an article up about Foursquare. Only it’s not about what Foursquare’s creators designed it for.

College students at University of Texas are tagging their campus with jokes, tips and gags. Not “tips” as in “I checked in on Foursquare and then left a tip.” No, students are leaving behind tags marking “the teacher they loathed,” “the room they smoked pot in,” and “the couch they had sex on.”

Awesome. Now THAT’S how you build an online grassroots community.

This is the kind of emergence that separates a Plurk from Twitter. Friendster from Facebook. Google Video from YouTube. To truly grow an online community, you have to get lucky and have one of these emergent lightning strikes. You have to encourage your community to use your product in a way you had NO IDEA existed.

If you’re really lucky, this emergent behavior will be self-replicating. For instance, “retweeting” and “follow friday”, had nothing to do with Twitter. They were created by the users. The exceptional part is how retweeting and follow friday reproduce themselves. If someone #Followfridays you, you are exposed to the trend. You then #Followfriday someone else. Other people see you tweet the tag. They do it to. It spreads faster than an chain email from your mom.

In the gaming space, World of Warcraft was amazing at promoting memes in its community. Blizzard did this by giving their massive player base a central place to talk – the Official WoW Forums – and making sure their customer service reps (Blues) allowed these memes to unfold. Want an example? Let’s melt some faces.

So there’s your answer, Foursquare. Give students easy ways to deface their colleges.