So is it Facebook vs. MySpace or Facebook vs. LinkedIn (or just one big Web mosh pit)?

As my fellow Time.com blogger Lisa Takeuchi Cullen reports, somebody from LinkedIn stopped by Time Thursday to try to convince people here to make more use of the professional networking site (or whatever you want to call it). I missed the tutorial, but I am a LinkedIn member (albeit one with a piddling 27 connections). A sample tip:

3. Check out a person's history.
You can learn a lot about someone on their profile page, if they let you (LinkedIn's "accounts and settings" function lets you set privacy controls). For instance, a little dinky called the "one-click reference" at the top of the page tells you all the people on the network who worked with the person at the company. That's hugely useful for journalists digging for sources, but also if you're expanding your business contacts.

Meanwhile, college-networking site Facebook has been working hard to graduate along with its users--and has been working especially hard to convince my former colleagues at Fortune that it can be a useful business tool. David Kirkpatrick has written an article and a couple of online columns lately about the company's attempt to make itself into what founder Mark Zuckerberg calls "an operating system" for users, and I've been getting lots of invites from Fortune people asking me to be their Facebook friend (I've been sending a few, too).

Lev Grossman (it's Link to Your Friends and Colleagues Day here at the Curious Capitalist!) mused a few days ago about the epic struggle between the rival online nations of Facebook and MySpace:

Facebook has historically been tight on policing its borders and maintaining civil order -- I think of it kinda like medieval Japan -- but with this new development it's showing signs of loosening up. MySpace is more like the U.S. right now: huge, free'n'easy and chaotic on the inside, and reasonably relaxed about its borders, with a few exceptions.

I'm not sure exactly how LinkedIn fits into Lev's nation-state metaphor. Its borders have always been less secure than Facebook's, but it is far less tolerant of frivolity than either Facebook or MySpace. Maybe it's Norway.

In any case, I'm of the impression that for grownups (at least grownups who aren't musicians or presidential candidates), the LinkedIn-Facebook rivalry will be far more relevant than anything MySpace does. Facebook is a vastly richer environment (I find out from LinkedIn when my friends change jobs; I get that on Facebook too, plus what music they're listening to, who they've recently befriended, etc.), but LinkedIn was designed for doing business.

Then again, why exactly is it that we need social networking sites to do business or anything else? Isn't the Internet itself the biggest, richest, most open social networking site of all? Are all these closed networks going to seem like AOL a few years down the road? No answers here. I've got to go check what's new on Facebook.