Well the Ad Campaigns used for both of these brands differ. Yelp chooses to go towards a whole video aspect but Foursquare chooses to promote their brand with an image. Videos tend to catch your attention more often well at least in my opinion, I am a video person I’ve always been interested in watching and listening then actually paying close attention to text. Yelp actually will grow faster for the simple fact that people prefer to watch then to read. Videos are entertaining and well photos are just blah… if you aren’t really interested in things like type or colors then an Ad campaign like the one foursquare introduced would not seem much appealing to you.
Promoting your brand is one thing but the way your promote your brand is another thing. The way you promote your brand is what will allow you to have a low amount of viewers vs a high amount of viewers.
Certainly the decision about what channels ie video, print, etc. to use for an ad campaign is an important one. That said, you didn’t write much about the imagery and tone of the two campaigns. You imply that the use of color and type in the foursquare campaign is not effective but don’t say how or why.