It was in June 2011 when Foursquare, the location-based social networking site, reached 10 million users.  And in under a year, Foursquare proudly announced that their user base has doubled to 20 million active users.

Also, to mark the third 4sqDay (April = 4, 4 squared is 16),  anyone who checks in today will receive the 2012 4sqDay badge as well as the following message:

“In 2010, foursquare fans declared April 16 4sqDay (4/4^2 – nerds after our own heart!). Two years and two billion check-ins later, you’re still why we get out of bed each day. Thanks to all 20 million of you for making us part of your lives. Happy 4sqDay!”

Foursquare has come a long way since its birth in 2009.  Facebook tried to buy them but failed, so they opted for the next best thing: they acquired Gowalla to make Facebook Places better than Foursquare.

Foursquare Top 10s

People use Foursquare to tell everyone what places they’ve been to, which pizza place serve the best pizza, or which hotel has the best service.  But the most interesting bit with regards to using Foursquare is that you have to chance to become Mayor of your favorite place on earth if you visit and check-in to that place enough times in a span of two months.  And you’ll stay Foursquare’s Mayor of that place until someone dethrones you.

So here’s the Top 10 best places with reigning Foursquare Mayors:

• The Great Sphinx of Giza – Egypt
• The Guinness Storehouse – Ireland
• The World of Coca-Cola – Atlanta, Georgia
• The Eiffel Tower – France
• Disneyland – Anaheim, California
• Facebook Headquarters – Palo Alto, California
• Brooklyn Bridge, New York, New York
• Experience Music Project/Science Fiction Museum – Seattle, Washington
• Stonehenge – England
• The Whitehouse – Washington D.C.

Most Foursquare users literally check-in wherever they go.  But there’s sharing, and then there’s TMI.  So here’s a list of places you probably should avoid checking into:

• Your house – alone or not, it’s not wise to share this info
• The bathroom – I know you’re thinking who would share that, but believe me, there are people who just love sharing every place they go to.
• Planned Parenthood – especially if you’re a teenager living with your parents, I don’t think a Foursquare check-in is the best way to tell your parents that you’re preggers.
• Strip club – Do I have to explain this one?
• Engagement ring store – If you’re planning to propose to your girlfriend, checking in would ruin the surprise. If you’re not proposing, this would probably result in a fight.
• Bridal store – unless you are getting married, checking in bridal stores isn’t a big deal.  But if you’re single and your friends see you check in, be prepared for hundreds of “Are you getting married?” questions.
• Jail
• Rehab
• Companies – when looking for a job, best not announce that you’re interviewing for different companies or if you plan on leaving your current company for a rival company.  It would be great if you don’t announce that.
• Anywhere but your house when you called in sick from work.

And if you’re looking to spend a romantic weekend with your special someone, here’s the Top 10 most romantic cities on Foursquare:

1. Lake Buena Vista, FL.
2. Napa, CA.
3. Venice, CA.
4. Saint Louis, MO.
5. New York, NY.
6. San Francisco, CA.
7. Reston, VA.
8. Beverly Hills, CA.
9. Myrtle Beach, SC.
10. Key West, FL.

And if there’s romantic cities, you can bet that there’s a list for the least romantic cities which are:

1. Beaverton, OR.
2. Bethlehem, PA.
3. Lawrenceville, GA.
4. Sterling Heights, MI.
5. West Chester, PA.
6. Normal, IL.
7. Norwalk, CT.
8. Tustin, CA.
9. Duluth, MN.
10. Waltham, MA.

There are a lot more places you can discover using Foursquare so go on and explore.  It might just surprise you.  Also, keep in mind that when using Foursquare and leaving a review, make sure you are telling the truth and not you’re not just having a bad day.  Your words could be the end of a business, worse, you could be sued for defamation.