Foursquare has 1.9m users, with 2 men for every woman

"As of today, Foursquare has just over 1.9 Million users. Gowalla has around 340,000.
- At its current pace, Foursquare will surpass 2 Million users within a week.
- Foursquare is adding almost 10x as many new users per day as Gowalla and, despite a significantly larger base, has a daily percentage growth rate that is 75% higher than Gowalla’s.
- Currently, Foursquare has about 5.6 Million venues and Gowalla has 1.4 Million venues.
- 1 in 3 venues on Foursquare have been checked into only once or never. That number is 1 in 4 on Gowalla.
- The most popular venue name is “Home,” followed by national fast food chains like “McDonald’s” and “Burger King”
- On Foursquare, men outnumber women almost 2-to-1. Exact gender breakouts are not available for Gowalla, but the most popular first names suggest a similar distribution."
Source: Article by Robert J. Moore, the CEO and co-founder of RJMetrics, using his company's data (rather than official data from the companies concerned), Techcrunch, 7th July 2010