Yahoo's new social network, Mash, is appropriately named. It feels like a mash-up of Facebook, MySpace, and Wikipedia. It's taken the best--or, at least, most popular--features from these services and put them together in a very compelling social service. I strongly doubt it will suffer the same fate of that other social network, the failing Yahoo 360.
Here's how Mash has borrowed from the best:
Facebook: There's a library of modules users can add to their pages. And the layout of the Mash pages is pretty strict, which preserves readability, especially if you turn off custom backgrounds. Yahoo plans to open up the module platform to developers, but it hasn't yet.
There are already some interesting modules, though. I like the MyMashLog feature, which, like MyBlogLog (which Yahoo acquired), collects the names of everyone who visits your page.
Wikipedia: The most interesting part of the Mash model is that, by default, your friends can edit your pages. Not just write on your wall, but really get in there and rearrange vital organs. Someone added a custom RSS feed (Webware, of course) to my page, for example. I returned the favor by putting a picture of a Mars Attacks action figure on his background.
As in Wikipedia, there's a revision history so users can roll back changes they don't like. There are also privacy options that let you lock down your pages.
Mash doesn't push a Twitter-like function, but there's a "blurt" box on each profile, and you can filter the "Pulse" feature, which lets you keep up with everything happening in your network, to show only blurts. That's pretty close.
At the moment there's no search, and, as far as I know, no mobile version. But as a public beta, Mash is impressive. It's fun to use and very fast to get into the system. The profile editor is also very slick and a pleasure to work with. It's also very easy to add friends.
During beta, you need an invitation to get into Mash. I've given away 25 invites already and am not handing out more just yet, sorry. You can also try InviteShare.