I should probably call this something other than a Twitter-like ecosystem, but that's what it is -- and that's the only thing to call it.
There's been a lot of discussion lately about whether a for-pay or ad-supported model works better. What's been overlooked is that there's a third option. Use the web.
It turns out that most of what's needed for something open that functions like Twitter is already out there, deployed, standardized, widely supported. There are a few things that need to be created, but not many.
I've got implementations of all of them. People are welcome to be plug-compatible. What I recommend is that no one try to do it all. That people pick off a component and try to do the best one possible, and connect up with the other components.
I've got some good stuff. Been working on it for a couple of years. I think you could do worse than having your networking stuff connect with mine.
1. For tweets, I use RSS 2.0 with the microblog namespace. My items don't have titles, because tweets don't have titles. So no Google Reader in this network, unless the adapt to feeds with items with no titles. The software I use for linkblogging is Radio2.
2. To read stuff, I like the river of news approach, always have. That happens to be more or less exactly how Twitter does it. There's a JSON format that defines what a river is. We had an open project a while back to create a browser for this format. I suggest if you're going to do a river, that you be plug-compatible with this JSON. Might as well have a little coral reef right there. My river software is River2.
3. To identify users -- please use DNS. It scales great. It's deployed everywhere. Amazon has Route 53 which is like a gift from heaven. Use DNS. I know it's hard, so let's make it easy. Look at current DNS tools as you would a command line interface. You can simplify it. I know you can! (I did...)
5. I use the cloud element in RSS 2.0 for pub-sub. Works great.
6. I think the part that's hard to scale is the notification. But the fallback is to poll. It's slow. Twitter will always be faster than the open system. But this will plug together like LEGO in ways Twitter never will. Unless they take this seriously, which they won't (they shouldn't).
6a. Twitter will always be faster, until they go down. I like to point out that RSS has never gone down once, and never will. Decentralized systems have that feature. It's a good one.
8. BTW, it has to hook into Twitter. Key point. The thing that's kept the other networks from working is that they don't peer with Twitter. Luckily this is in keeping with the new Twitter mandate of putting stuff in but not taking stuff out. Great. If you want to read what someone says on Twitter you have to use Twitter. Not a big deal it turns out.
I'm sure I'll add more items to this list, and hot-up the names to the docs and software. In the meantime I have to admit even to me it sounds pretty exciting and I've been immersed in this for quite some time.