Business or content providers cannot write snippets, unless the snippets are real, independent, and an unpaid review.
Reviews have to permit both good and bad reviews by customers. Reviews cannot be inspected or restricted by business/content provider before being submitted to Google.
Reviews can’t be sentences built off of automated metrics or from data. The following would not be acceptable: “The average person, based off of X number of replies, experienced Y with this business/product.”
Reviews for business with multiple-locations (franchises, etc.) may only be submitted for the exact location they were written/intended for. In other word, reviews cannot be applied towards all locations for the same company.
Content providers/aggregators cannot have any paid agreements with the business in question to provide reviews.
Duplicate or similar reviews across many businesses may not be included.
Reviews from your site may be included, but not reviews from syndicated sites or third-party sites.
The big shift is in the event you do include third-party that are not “directly produced by your site,” do not mark up those reviews with schema. Only mark with schema if it’s “directly produced by your site, not reviews from third-party sites or syndicated reviews.”
Local review markups from websites will be impacted greatly by these changes.