Disable firefox popup blocker? ...what the

I’m running Firefox 3.0.1 on Ubuntu Linux and it seems to me that there’s no way to really disable the popup blocker.
I have added the domain into the “allowed” list and I’ve unchecked “Block popup windows” in the preferences but it seems to me that firefox still blocks popups which aren’t triggered by a user event.

For example:
If I open up the firebug console on any site and enter

window.open('about:blank', 'foo');

It works.

But If I do


foo = function() { window.open('about:blank', 'foo'+Math.random()); }
setInterval(foo, 1000);

It opens the first one, then starts blocking each one and I get the “Firefox has prevented this site from opening a pop-up window” bar at the top.

What gives?