Facebook has been changing its way of presentation to everyone (e.g. the move from wall to timeline) and most of these changes while appearing cosmetic has actually brought with them differences in content presentation. I don't mean just the way the content is presented. I'm talking about WHAT is presented.
A typical active user, which is what I consider myself to be, would have an upward of 500+ friends. I have ~700, and I have friends who have above 1k. This.... isn't reflected on the News Feed. Think about it. How many people's posts do you see there? 20? 30? Maybe 50 different people? That is but <10% of all your "friends" (mine are actually friends since I don't add anyone I don't know and met, but I think there are people who do). Even if we assume that at least half of the people are inactive (i.e. they don't post anything for more than 24hrs at a time), that number only rises by double, which is only a bit since it was small to begin with.
While I can't say statistically how much the algorithm that brings you posts called "highlights" (which is the default option, as opposed to the other one which is to bring you the newest ones) actually throws away stuff that are supposed to appear, I know it's quite a significant amount from personal experience.
Photos of holidays which some people have asked me about after I came back in this way like
Friend: Hey you went there so how was it?
Me: Yeah, it was great! I put up the photos already, didn't you see it?
Friend: No... I didn't. When did you put them up?
Me: About 2 days ago already...
Friend: Really? I haven't seen anything like that...
And these are active people on Facebook. Occasionally, I'll happen to wonder why someone isn't posting even though I remember that person to be a regular, only to discover upon visiting their wall that the News Feed wasn't picking it up. It's quite terrible.
I think this has only been a problem ever since they mirrored the Facebook header (notifications are now on the right instead of left). Of course, I'm not implying that that's the cause (if for some reason you're wondering).
I have come to a conclusion that the most recent algorithms in the News Feed are hyper-sensitive to interactions, which is not something I like at all. In fact, I absolutely hate this set of algorithms. Here's how I think it works:
Every like, every comment, every share, every click on a link shared, (basically every single interaction you make with any post that's not yours) is recorded and given some score (which may vary, e.g. a like could be worth less than a comment). This score is held by each of your "friends" and possibly "pages" that you're subscribed to. The score affects how often you see their posts appearing on your news feed.
This score also degrades over time, causing people whom you rarely interact with to disappear from your feed altogether. People whom you have low scores with will only have their posts appear on your feed if the posts have a high score (so there are two sets of scores to think about). For a post to have a high score, it must generate lots of activity, say, number of likes or comments. I conclude this from the fact that the people whom I interact with the most tend to comment and "like" stuff that I post, and then suddenly, after a certain amount of likes and comments, the post seems to reach other people whom I don't interact with as much, and they start to join in the comment stream or "like" the post.
This way of managing the News Feed might seem pretty good, but what I have gripe with, is likely, the rate at which "relation" scores with people degrade.
It's too fucking fast.
There are quite a number of friends whom I am interested to know what they're doing, but don't want to bother to leave a comment (since it's along the lines of "oh, that's nice") or a "like" (since it's not quite something I'd like) and these people disappear easily from my feed. Now you may be asking why I'm so interested in following them, and if I really wanted to, there are options for it. True, but also false.
Firstly, why I want to follow them is along the lines of the same reason one might want to see what interesting things an avid traveler might post up, but then, daily life (when not traveling) is probably boring and not worth the time to read. No one I know travels every month, and that's about as long as it takes for someone to drop out of my feed due to the score attrition. Going by this system, once a person drops out, it becomes a self-sustaining cycle, and that person will never come back right? That's a problem, but Facebook has a solution of course.
That's another part of the algorithm that I noticed. Facebook, will, randomly pick one of your "friends" whom you don't interact with often, to show on your feed to give you a chance to restore interactivity. (For a good analogy, in bittorrent protocol, such behaviour is known as "Optimistic Unchoking".) However, the chances of that happening are low. I've noticed only 1 or 2 people randomly appearing now and then. That's like 1/700 chance per day that I'd get any particular person. So back to the guy whom I would like to receive regular updates. I won't see him for a very long time, if ever.
Secondly, Facebook doesn't have a way of subscribing to a people to ENSURE that their posts appear on the news feed. Even after checking the option "follow", posts still don't stay. (I've just checked to confirm that.) The other option, is to tag on the "notify me everytime this person posts" to a particular "friend". That's a problem if that person posts around 10-20 times a day, or if you decide to follow several people that amount to that many posts a day, which is extremely easy to do.
All in all, this means a very screwed up News Feed, and the whole "social networking" thing is quite lost. Instead, Facebook focuses on bringing you "Pages" (notice the suggestions everytime you "like" some link or page?) which is where it makes money from. It is taking away peer-to-peer interaction in place of organisation-peer interaction.
To recover my News Feed, it takes quite a bit of maintenance. I have to try find posts to interact with of people whom I want to receive updates from. I am forced to just click a "like" here and there to ensure that my feed stays the way I want it to be. Now and then, I have to sift through my friend list to try re-establish some connectivity again. This is labourious.