Define optimally. Seriously, there is always going to be some easily measurable value(s) that will operate as a proxy for "optimal". Even if the model perfectly maximizes the goodness of the proxy values for every customer, the model will still be wrong inasmuch as the proxies are divorced from the actual "optimal". Also, if optimal-ness is focused entirely on maximizing revenue under the current model, the result will be a an automated user-abuse mechanism that entraps the user and forces them to put up with a horrible experience just to eke out a 3% boost in ad impressions and the 0.003% boost in clicks that generates.

And I hate, hate, hate that aspect of Facebook. God forbid you should ever want to find a post a second time. God forbid I should see posts from my friends in a timely manner. Nah, show me posts from banks and cell phone companies that I will not do business with, ever, and show them 50 times.

YouTube Autoplay is a pain in my ass that I keep having to disable.

It's too bad we weren't responsible enough to manage Usenet and email in a Spam-free way. Now we've driven ourselves into a walled-garden, crappy version of Usenet with proprietary clients that serve only the site operators. At least we know where the spam comes from...