There are a bunch of comments here expressing outrage at the seeming arbitrary decision of Apple to pull this app. Whilst others have correctly pointed out tha

There are a bunch of comments here expressing outrage at the seeming arbitrary decision of Apple to pull this app. Whilst others have correctly pointed out that the app no longer works because FourSquare has cut off API access, Apple's policies do essentially allow them to remove apps that they consider to be in bad taste or against the interests of consumers without having a guideline in place in advance. They explicitly say that the app store guidelines are open to being changed, and that they think developers should know where to draw the line, even if it's not in already in the rules. Compliance with the stated rules isn't a guarantee of anything. They really just help people to avoid repeating things that have caused rejections in the past.