This reminds me that Youtube used to have a star rating system, but as you say, it was effectively treated as thumbs up/thumbs down, so they eventually made that official.
Interestingly though it wasn't quite a simple five stars/one star dichotomy: the original blog post[0] has a dead image, but this one[1] shows that while five stars was overwhelmingly the most common rating, one star and four stars were about equal in second place.