I think people have to be a bit limited to rate 'anything by Bjork' as the worst song ever written. I mean, sure you may not like her stuff, but 'worst ever' surely can't include things that are innovative and interesting even if they are a bit too challenging for some. It implies a truly unimaginable degree of awfulness, surely?
Does no-one remember the abominable
Vanilla? Weren't they put together as bet to see if some producers could get the most talentless people they could find in the charts?