Foursquare (Wikipedia explanation) launched in London on October 8th - 3 weeks on, how many people are using it?

When I checked in at the Emirates on Saturday for Arsenal's 3-0 triumph, I was made mayor of the Emirates (although someone else has now taken the mayorship).

My foursquare badges

More interestingly, Fouraquare said three other people were checked in there.

The attendance was 60,103. And according to Wolfram Alpha, the population of London is 7.42 million.

So if 4 out of 60,103 were checking in, that means out of 7.42 million Londoners, a total of, er, 494 people are using it.

Some caveats

• The Arsenal crowd may not be representative of Foursquare users.
• It also includes lots of people who don't live in London (but they visit London, clearly).
• People may have had trouble accessing the mobile web to check in (as it's often erratic around the Emirates on match day due to the number of people using it).
• Then again, the incentive to become mayor of the Emirates may have made people more likely to check in.