Comment 15 for bug 1009816

The old behaviour was likable for the same reason that the "open links in new tab in the background" option is likable (and is the default these days): it allows one to open a link without immediately context switching to it; instead one can continue with the task at hand, and switch at one's own time (and the flashing taskbar entry makes this easier). So personally I think it makes more sense for the implemented behaviour to be consistent with the value of the aforementioned setting, not with the startup behaviour.

I too was surprised when the new version of firefox started behaving in a new, surprising way, and I came to bugzilla to look for or file a bug.

Anyway, just my $0.02. Just because the old behaviour was the artifact of bug does not automatically mean it's not the desirable one. But of course it's up to the developers to decide what they want to implement.