Mazda sold 100 cars at a 20% discount as part of a Facebook Deals promotion

"The ability to attract the attention of smartphone users making local check-ins. Clothing retailer The Gap gave away 10,000 pairs of jeans to the first 10,000 customers to use the Facebook local check-in service, and Mazda sold 100 cars--exceeding expectations--with a 20-percent-off offer at five U.K. auto dealerships, Haines said."
Source:  Facebook UK's Stephen Haines, reported by CNet, 2nd March 2011