Yelp TOS: https://www.yelp.com/developers/api_terms
"You agree that you will not, and will not assist or enable others to: cache, record, pre-fetch, or otherwise store any portion of the Yelp Content, or attempt or provide a means to execute any "bulk download" operations, other than storing Yelp business IDs which you may use solely for back-end matching purposes;"
It looks like you're storing Yelp Content. Or maybe reviews aren't "Yelp Content" specifically? Or did you get a written waiver for this service?
Or does no one ever give a toss about these TOS, and just complain on twitter when they get API access revoked?