I could be wrong, but I don't think userscripts does any significant culling of their catalog; downloading an arbitrary script from there is just as dangerous as anywhere else. This whole thing is just silly, you have to confirm the installation of a javascript extension. If you accept that it's your responsibility if it turns out to be a keylogger or what have you, not the Chrome team's. They're shooting everyone in the foot because someone might accidentally shoot their eye out.