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.

I have this exact problem with a lot of extensions I would like to use, so I only actually use one that extension which I implicitly trust anyway, LastPass. Here's an example, I use both Mac and Linux but on Linux I would like to have a more native looking scrollbar. Such functionality exist as extensions but I really do not want to trust a scrollbar plugin to have access to all data on all my websites (this is the permission required). I have been slowly (painfully) moving back towards Firefox recently just because on Linux Chrome is so out of place, but the Chrome Dev Tools are still way better.

So why do you trust Chrome in the first place?

I assume that Google is giving me a free browser because it will drive traffic and revenue to the search engine. There is no reason for Google to be nefarious to make money.

I cannot guess the motivations of free plugin developers.

Stylish is GPL v3, according to the FF addon page.

Google's most valuable asset is its reputation; switching cost are still pretty low for most of their properties. But, not only does Google have a disincentive for being nefarious in that fashion, they're also under more scrutiny vis-à-vis Chrome (which would be effective even if it were not open source).

> they're also under more scrutiny vis-à-vis Chrome (which would be effective even if it were not open source).

Chrome is not open source. Chromium is, but they are not the same.

You think Google would steal my banking information or my identity?