If you look at their wikipedia page, the section 'criticism' [1] lists a variety of issues. You'd expect criticism from incumbent taxi companies, and perhaps you also expect sketchy labor practices, and a few fatal accidents and rapes. But the problems also include user privacy issues, threats to journalists, and attempts to sabotage their competitors.
[1] https://en.wikipedia.org/w/index.php?title=Uber_%28company%2...