The problem with Stylish is the same problem with every other chrome extension. It can access all your data on all websites. It can surreptitiously autoupdate. I wouldn't want a person I knew to look over my shoulder while typing in my banking password, but I'm going to trust this extension with everything? I have ghostery and ad-block plus, and that's scary enough. That's it, that and my own extensions. I don't know anything about who made Stylish.