every user I talk to now seems to think that Facebook is going downhill and increasingly making decisions that benefit their stock holders rather than their users
Why would you expect them not to? Facebook is a publicly traded company; they have to make decisions that benefit their stockholders or they will go bankrupt.
Also, Facebook's users are not customers; Facebook gets its revenue from ads, not users. So benefiting users only helps them if it increases their ad revenue. That might happen indirectly if an improvement to the FB user interface gets them more users or keeps existing users on the site longer so they see more ads. But FB already has a billion users, and many of them already seem to spend most of their available free time on FB, so the relative benefit to FB from improving the UI is going to be pretty small.
Finally, I think it's worth mentioning a historical parallel that seems relevant to me. I believe pg mentioned in one of his essays that many companies who made third-party Windows software ended up basically doing market research for Microsoft: MS just took all the popular features from third-party apps and added them to their own apps. Developers of FB apps like SocialFixer seem to me to be in a similar position. Caveat programmer. :-)
[Edit: I see that the "End of the Power User" article that was linked to hits some of these same points.]