It has a stratospheric valuation, an Oscar-nominated movie about it, 600 million fans, and its CEO just appeared on Saturday Night Live. So where's Facebook going to go from here? Down.

Okay, so maybe not right away.

But it certainly feels like the social-networking site is beginning to sag under its own ponderous weight and prodigious Netscape-era hype. In fact, Facebook is so overhyped that a recent $1.5 billion injection of capital from Goldman, Sachs and others meant it now has an estimated market valuation of approximately $50 billion.

Indeed, Facebook could be even bigger based on trading in the secondary market (the one for wealthy folks) where according to SharesPost the company is worth over $82 billion -- making it more valuable than Amazon.com.

But it seems like Facebook's days may already be numbered. Why? Facebook started out as a simple, fun place to digitally cavort and post silly, unflattering pictures of one another. It quickly transformed into a miasma of lurking dangers, threats to our personal security and safety, and a great way to get fired -- or worse, prosecuted for goodness-knows-what. Everyone should be a little more cautious about the "social" part of social networking, these days, and for good reason.

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Jilted partners use Facebook to stalk the objects of their unrequited love. Mean girls use it for cyberbullying. Avaricious divorce lawyers use it to skewer fighting couples and tip the balance in child-custody battles. The police use it to catch criminals. Criminals use it to find out when victims are away from home and rob them. With FB friends like these, who needs FB?

Even the relatively innocent concept of posting a cheerful picture on the site has become fraught with potential disaster. The problem is that photos are often tagged with date and location information, which it is not necessarily a good thing to share if the pic is of your fancy car parked in front of your home (as a member of the Mythbusters TV show discovered).

More disturbing yet, face-recognition algorithms are being applied to some photos online. So if someone has identified you in one photo, programs may fan out and automatically tag you in others (at least one erroneous photo of me keeps cropping up online, putting me at an event that I did not in fact attend).

Perhaps Facebook's biggest problem, however, is that it's too bloated to manage any more. Just ask yourself how many times you've hesitated to post some snarky remark because it might be misinterpreted by some FB "friends"? Or thought twice about sharing a vacation picture because an old boyfriend or girlfriend or jealous business colleague might see it? Or even decided not to add a funny shot of your child to your digital album because, well, you don't know who's out there.

The truth is, once you accumulate a certain number of FB friends, you can't be sure who will see what you post -- or what they're going to do with it. And that's Facebook's biggest problem going forward.

Facebook fans will point out that there are ways to solve these social-networking problems. You can set up multiple accounts, for example, and use one profile for business, another for friends. Or you can restrict subgroups of friends from seeing certain comments or pictures by setting up separate friend lists.

In other words, you can create one list of only family members, another list of business friends, and presumably another list of your "real" friends. Then when you post something, you only post it to the appropriate list (a photo of you playing beer pong, friends only; a shot of you moderating an important business panel, definitely family friendly).

There are several problems with this approach, however. It's about as easy to use as the blinking cursor on an old-school computer -- and about as much fun. It's also not reliable; Facebook keeps changing its privacy settings, so unless you stay on top of the changes you may end up sharing more than you planned.

Moreover, managing a variety of lists can quickly become a part-time job. You have to remember to move people from one list to another, should their relationship with you change; today's friend is tomorrow's frenemy, after all. And just try explaining to someone why they are on the "co-workers" list and not on your "friends" list. Even remembering who is on which list is a problem.

Complexity is the enemy of social networking, and complexity is killing Facebook. The beauty of the ancient bulletin board systems from the eighties was that there were so few people on them you didn't need to worry. And no one thought about using something you posted against you in a job interview; they flamed you in ALL CAPS and that was that.

Facebook realizes it has a problem. There's already a "what's the next big thing?" vibe permeating its pages, as if everyone knows we've stopped honestly sharing things on the site because we're either too fearful or simply tired of friending and unfriending romantic partners (or just unfriending people who post too many funny possum videos -- you know who you are).

So the site is trying its hand at e-mail. It's also trying to work more closely with the world's largest Internet calling service, Skype, and in the process made exactly the same mistakes as eBay. It's even tried to mimic location-based services like Foursquare. None of these moves has been particularly successful.

On the other hand, when Facebook tries to use all that valuable customer information it has accumulated to make money, users holler bloody murder -- and security experts decry any changes as an incursion against our personal liberties. Just wait until Netflix connects to Facebook and the company tries to track all the movies and programs you watch. When you're as big as Facebook, people notice when you start selling their likes and dislikes.

So you can't use Facebook for fun any more. It's also not really for business. And it certainly isn't a safe place to pick up a date. So is the Facebook fad already over?

A lot of big money is betting that the answer is "not yet." But there's no such thing as brand loyalty on the Internet. Remember Prodigy? Remember Pointcast? Remember AOL and Yahoo? They were are all darlings of the digital age, too.

FB friends can be fickle, and if people from my list of truly cool FB friends join another site, I'll probably go too. After all, nobody wants to miss the next big thing.

Follow John R. Quain on Twitter @jqontech or find more tech coverage at J-Q.com.