It looks like Firefox is moving to a compatible-by-default model for extensions. I find this interesting, since I proposed this back in 2004 to no avail.
To be clear, I don’t mean to say that compatible-by-default would have been the right choice in 2004… Predictions about the past are almost hard as predictions about the future, and at least two major factors have changed since then. First, the state of the world for extensions now is more stable than it was in the Firefox 1.0 timeframe. And second, Firefox’s rapid release cycle exacerbates spurious compatibility problems, making this proposal significantly more attractive.
Hurray! Hurray! The people of good finally prevail!