I think they're completely fine with it. Foursquare has been extremely open about how people use their API and this is what their API is for. In the end I don't

I think they're completely fine with it. Foursquare has been extremely open about how people use their API and this is what their API is for. In the end I don't think they care how people are checking in. They're still gathering useful location information for businesses which is their real value add.