Foursquare venue ratings are calculated from a wide variety of signals derived from users' interactions with that venue. Explicit feedback of the form you mentioned is the easiest: liking or disliking a venue, or leaving a positive or negative tip. read more
On their page (Place Ratings) they say: "A place’s rating is based on a number of signals that we’ve gathered from our social data mines, likes and dislikes, and from positive and negative tips". read more
Foursquare venue ratings are calculated from a wide variety of signals derived from users' interactions with that venue. Explicit feedback of the form you mentioned is the easiest: liking or disliking a venue, or leaving a positive or negative tip. read more
You need to check out the latex work on pages 5 and 6. A couple years ago, Stephanie and I collaborated on a poster about trending venues in Foursquare, which is an important component of the ratings for new venues. read more