To be fair RSS was hitting mainstream when it go whacked. It was where Bluetooth was right before the headset rage set in (2003?) and pulled it out of the limbo it had been in between the wants of nerds and the cheapness of manufacturers and most consumers. The 4 factors that hurt RSS in my mind were: 1. non-obvious pronunciation to laymen/not memorable name- even Bluetooth, Firefox, and Google are easier to remember. 2. Similarly it's lack of corporate co-opting and the ensuing pitch as the "next big thing"; good or bad this often pushes tech into the public eye. 4. The post-Chrome seemingly desperate obsession of existing browser providers to seem hip by eliminating and UI elements not used 100% of users. If back and forwards buttons are tossed in the dumpster RSS had no chance in hell. And finally, like you suggested a bit of 1 + 2 in Facebook. A good enough, and for casual users simpler integrated option that also worked for other needs like photo sharing and discussion postings in a presumed safe environment.
