Yelp and Tripadvisor are probably getting a bit worried with Google pushing their map service more and more (or at least they should be). Google Maps already has pretty much, every known business on the planet listed. Try it out, search the name of an establishment with the name of the city it's in. I'm guessing 9 out of 10 times, that place will come up in the results. What you may have started to notice is that users are reviewing these places right through the Google Maps app. I have been using Google's star/save feature for years now. This feature was once limited to only the web browser version of Google Maps, but Google has recently rolled it out to their mobile app platform as well.