File this under, “duh.” Like anything computer-related — the more you add, the slower it’s going to get. I’m not surprised that Mozilla’s automated testing found that Firebug was one of the worst offenders in slowing down the Mozilla browser, but honestly, if it weren’t for Firebug, I wouldn’t run Firefox at all these days.
One of my other favorite add-ons made the top ten as well — Xmarks Sync at #9. But again, I’ll take a slower startup time for the functionality of the add-on.
