Thoughts:

So ... if Facebook didn't exist, in 2500 the year 2000 would just be a pleasant memory instead of a historical reality?

Presumes the only thing we'll have is Facebook, when in fact we'll have oh so very much more. Also presumes that Facebook is an impartial observer of life, which Marshall McLuhan would sternly disagree with. The point of my post is that the environment of Facebook is its own perspective, and that perspective is one of lies and triviality. In other words, were the world of 2500 to only know us through Facebook, they would have an incorrect and detrimental view of us.

Dismissing Facebook as a trivial place is clearly wrong; it both is and isn't.

An allegation, not an argument. Facebook is a trivial place. Through it, trivial things are made important and important things are made trivial. It is a filter through which perception is altered to fit the perpetual need to "share." When we "share" everything, the things that we should share are drowned out by the things we shouldn't, and the things we shouldn't broaden and cheapen the discourse to the point where we no longer trust our social instincts.

There's a famous old diary written by an English clergyman or similar, wherein he wrote down everything he ate every day for multiple decades in meticulous detail.

It is famous for existing, not for what it contains. Lichtenberg's Waste Books, on the other hand, are famous for what they contain... which is the day-to-day scribblings of a philosopher-scientist.

On the other hand there's Shakespeare, whose handwriting survives in something like six places, all signatures.

And to you, Shakespeare is Shakespeare and the clergyman is "an English clergyman or similar." Shakespeare shared the shit that mattered.

If Facebook had been around in 1600, I wouldn't give any more of a damn about what British clergymen ate for lunch, but I would sure know a lot more about Shakespeare.

I don't think you would. The fact that we know a hell of a lot more about lesser figures of the same era, despite the fact that Shakespeare was celebrated in his own time as much as he is in ours, illustrates that the man valued his privacy.

So I don't think your analogy really works.

I think you don't want it to work.

Facebook has caused me to feel disgust for many people I've met, and also to respect many people I met never have realized were interesting.

So on balance, it's a null. Although why we "friend" people we don't respect is a bit of a mystery, I'll admit... while also pointing out that it's a big part of the problem.

Some people spew bullshit, others make posts that in 500 years could easily be seen as valid anthropological record.

And without Facebook, history would forget the bullshitters. The 500-year-post folks?

I guarantee that they have outlets other than Facebook.