I have to share this superb campaign by GroupOn competitor, Living Social.

We’ve all seen the branded London black cabs, but the campaign normally stops with the outside of the vehicle. In this case, unsuspecting passengers were invited to make a choice — carry on to their original destination, or ‘roll the dice’ and go for an exciting experience.

Okay, it helps when you have a large budget, but you have to love this kind of innovation. This kind of viral marketing success is hard to pull off, but this campaign hits the mark beautifully.