Too many software developers just can't bring themselves to implement completely invisible features. They need to show off about what a great feature they just implemented, even at the cost of confusing people. Really great UI design disappears. →
The problem that Namespaces were introduced into RSS to solve was: lots of different people want to add their own custom extensions to RSS. Since RSS is such a small domain, the chances of two people coming up with identical tags with different semantics is actually quite high. →