Yelp already is one of the 45th most trafficked website in the US (Alexa). With millions of users already on the site with the intent of finding a restaurant,

Yelp already is one of the 45th most trafficked website in the US (Alexa). With millions of users already on the site with the intent of finding a restaurant, bar, mechanic, spa etc., adding a daily deal and leveraging their traffic makes sense. How much should groupon worry?