Why aren't there more?
The biggest problem is resources. There are many people I know who are as talented as heck, but don't have enough resources to show off their skills and develop what they have in mind. Take Stephen here for example. He's today easily at the forefront of lightweight application development, and was recently acknowledged for the same. If you read that interview, you'd see how important the fact that Ning was free, was. If it was like other services, and charged from the ground up, we would probably have never seen a Stephen. Well, not until he got enough resources at least!
So, why should only people with the money be allowed to be counted among the cream of web developers? Any serious developer takes pains to learn their language and then apply it. That should be reason enough for them to be given the suitable conditions and resources to allow them to write and program the way they want to.
The helping hand
We need more services like Ning, which tackle various aspects of Web Development, and offer everything which a prospective developer might need. All the person now needs to bring, is the knowledge and skills. Thats not such a small thing to bring, but atleast a person like that won't be hardpressed for resources to make what they want to.
Even if the developer just has one thing to contribute, there's nothing to say that someone else won't use that to start something new. This is where Ning excels, by offering the ability to clone apps and use them. Ofcourse, Ning hasn't been utilised properly ever since its entered the market except by a few handful of people. But its those handfuls who might make tomorrow's next killer application, with the skills they develop and gain by working on small apps at Ning.
A playground of geeks
A repository of modules, ready to use widgets, blocks of code, classes, methods ... in short all the resources that a developer could need is what is going to be probably the next big area for companies to tackle. An Integrated Development Environment for the web will be the next bookmarking/tagging phenomenon. Atleast, it should be. There is nothing to lose from this, only lots and lots of gains.
The only resources that a service like this needs is lots and lots of space and a decent amount of bandwidth. We know that Yahoo! and Google are both in the best spot to launch a service like this of their own, or probably acquire one and give it the boost it needs.
Create the ultimate playground for geeks to thrash about in, and they'll come aplenty. There are ideas just waiting for a stage with the right equipment. One of them, might revolutionise the internet again, who knows!