[masklinn]

extensions in general are a huge issue for all browsers, it's easy to install a bunch of them and not notice your performances going down until a few months later, at which point you blame the browser (even for developers, evaluating the performance impact of extensions can be difficult).

That's especially true for content-alteration extensions like ad-blockers as it's very easy to implement them in ways which work well enough with few rules but degrade superlinearly at scale. That's a big part of the issues Firefox has/had (not to mention the "depth" available to XUL extensions), but it's not like other browsers are immune.

[tajen]

One shouldn't let an extension with access to all the pages run continuously. I wait for the day a famous extension like Awesome Screenshot will be pirated and publish everyone's bank account credentials...

Of course, between "should" and the reality, there's room for tolerance.