This depends on the type of networking you wish to do.

Myspace is still the best place to go if your networking consist of anything music related (I do work for a couple record labels with Street Team Marketing and have found this to be the best place for our work).

Facebook/Twitter (I combine these together since they can talk well with eachother) seem to be the best option when looking to network with Friends/Family.

Twitter is also a great source if you are looking to "network" in a way that you want to talk with your customers and give them a chance to feel connected to your business/product.

It depends. The only thing I've ever found Myspace useful for is for music. The site's horrid-looking and clunky, but it IS really easy to discover new bads for.

Facebook's best for people you know in real life, because it's closed -- random strangers can't just look up your personal information, and there tends to be a lot more of it there. Plus, communication is much easier.

And Twitter's best for the public at large. There's less personal information, usually, and the focus is on information and personality.

Twitter is just a phone call in print;
since "instant messaging" (IM) has been around long before the advent of Twitter,
I am astonished that anyone would even bother with Twitter.
That it has become something of a phenomenon merely makes it the latest fad,
designed for people with short attention spans and no social lives.
I deleted my account.

I was swamped with unwanted attention in MySpace,
vis-a-vis alleged teenyboppers, druggies, racists, profanities,
"girls" half my age wanting dates, etcetera ad nauseum,
so I cancelled my account. Nuff said.

Of the list you gave, Facebook is superior, IMHO, but that isn't saying much!
You may view the people you have something in common with or are otherwise interested in;
likewise with the "groups" you can join.
I found lots of people I recognized and who remembered me,
but, as with any other social intercourse,
even the best "conversations" end, leaving nothing to say,
and wondering why in the world one bothered in the first place!

Having said all that, I have found all these sites to be difficult to figure out or navigate.
Facebook does not allow you to edit anything you post on your wall;
yes, you can remove and re-enter it, but what's the point of re-inventing the wheel?
You don't get any "points" for doing so,
and nearly every other site I know of lets you edit just about everything,
so why doesn't Facebook???
Delete, but not edit . . . say WHAT?!?!?
Also, adding/changing pictures, or searching for friends/etc is like pulling teeth
(you can only view 10 people or groups at a time;
one search I had claimed to have over 5000 results!
That's 500 pages/clicks I would have had to endure!).

For all these sites (and LOTS more!),
it seems that the engineering maxim "KISS" (Keep It Simple, Stupid!)
has long gone by the wayside.

Forget virtual social networking . . .
go out with your real friends (or find some!),
or read a nice book,
or something else . . . ANYTHING else!
Just keep it "real", okay? ;)

I would say Facebook is best for networking. It's my social network of choice anyway for maintaining relationships with my friends and family, most of which are scattered across the country and a few who are overseas.

For business networking, I'd say that Facebook could be used but with caution. Many employers are looking for any signs on your Facebook page that suggest you may be a liability rather than an asset. And let's face it, you don't have complete control over your friends or your family posting embarrassing photos of you. If you're already employed and you are comfortable with your work environment, it's all the better. You can mix it up and communicate with colleagues. You can use it as an event board or start a group that your colleagues and you all participate in and discuss whatever project you're working to complete from the comfort of your desk.

I agree that for music networking, MySpace is the better place to go! By far, but it ranks low on personal and professional side of online networking. Twitter is kind of annoying in that it can be too personal and usually allows for people to post way too much information about themselves as they go through their day. However, it is a powerful marketing tool if you have followers who are willing to repost updates and provide you with the exposure your business needs.

Really it boils down to what type of networking you're wanting to do.

Open, friendly networking: Facebook and Twitter.
Business networking: Facebook groups with respect to personal page privacy and non-judgment.
Music business networking: MySpace.
Product/Service Marketing: Twitter.

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12 Oct 2009 ... Facebook recently incorporated Twitter-style '@' tags for ... MySpace retains the title for the social networking site that users spend ... Get The Best Shopping Deal Without Hours of Searching. ... Opinions expressed by the Advisors are their own and do not necessarily reflect the views of Yahoo! ...
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I find that for business purposes Twitter is the best social networking site. This is because it lets you advertise and connect with others in real time. It also allows you to track those who are talking about your brand and use these comments for customer service purposes or as testimonials.