There were over 600,000 check ins at London 2012 Olympic venues on Facebook

This just in. 623,957 check ins to Olympic venues during the Olympic Games on Facebook. About 10% of that number on Foursquare.
— Alex Balfour (@AlexBalfour2012) September 2, 2012

Note - Alex Balfour is Head of New Media, London Olympic and Paralympic Games 2012