Here's a sneaky little Foursquare stunt: Euro RSCG Brussels, with help from generally mischievous agency Duval Guillaume, claims that it recently became Foursquare mayor of 42 rival ad agencies in Belgium—simply by visiting them day after day and checking in. There was a recruitment element to this. When Euro would become mayor of any agency, it would post an update on Facebook and include an appeal to digital creatives to consider joining the company. It's kind of a fun, subversive idea—but seems like a whole lot of work for possibly scant reward. Notably, the case-study video says nothing about whether the stunt brought in a single new employee. Adverblog via Brainstorm9.