Facebook is very useful for messaging, and that would be sufficient reason for me to use it.
I find that it is also useful for following local businesses and organizations that are of interest to me.
Facebook reminds me of the birthdays of people I am friends with, which is the only way that I can remember anyone's birthday; this has sometimes been useful socially.
Once you collect some interesting friends, you may learn stuff from Facebook feeds that you don't learn elsewhere. This is hit-or-miss though. Facebook was how I discovered Wait But Why.
I also post to Facebook, primarily because I am friends with a lot of people who are part of a very limited culture -- most of my coworkers and local friends get exposed to very few ideas outside of church and office gossip, which means that many of them never see a rationality blog post, see anyone they know support marriage equality publicly, never see anything interesting regarding technology (other than consumer products), etc. I doubt that many people enjoy my posts who don't have other sources of finding interesting things, but I think that it is probably useful to expose as many people as possible to things like this -- otherwise they might go through life thinking that football, dieting, and pictures of their kids are all that anyone ever thinks about. Yes, I realize that championing Facebook as an agent of social change is totes feeb, but whatevs.
Isn't facebook strictly inferior to email for messaging? By a wide margin? It's not archivable, sortable, filterable, searchable, forwardable, or manageable. It can't be sent to multiple recipients. It has no BCC, threading, prioritizing.
This thread is for asking the rationalist community for practical advice. It's inspired by the stupid questions series, but with an explicit focus on instrumental rationality.
Questions ranging from easy ("this is probably trivial for half the people on this site") to hard ("maybe someone here has a good answer, but probably not") are welcome. However, please stick to problems that you actually face or anticipate facing soon, not hypotheticals.
As with the stupid questions thread, don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better, and please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
(See also the Boring Advice Repository)