The default search engine!
Ok it does make sense Firefox gets a ton of money from it but it still sucks. Come use our private search engine and escape from google, actually google is our default search engine there is no escaping (manacle laughter!)
Also I believe betterfox + ublock origin should be the default Firefox config. I have used betterfox for nearly 2 years now and I have NEVER had any issues with websites breaking.