Google Play is constantly tweaking the Google Play store, this time around it’s the user rating system that’s seen a change with Google removing the thumbs down as an option on user reviews.
Previously when reading a review you could thumbs down a review if you felt it was unhelpful or misleading, or if it was helpful thumbs up a review if it helped you. In a change that appears to be rolling out slowly through a server-side switch Google has removed the thumbs down option, with the new thumbs up icon now larger and easier to see and hit.
You can still sort reviews by age (newest first), or see the most helpful or highly rated first, you just can’t give that whinger who is complaining about something not even to do with the app he’s an idiot with a thumbs down any more.