Netscape, Ning and developing platforms
Marc Andreessen pitched Netscape to developers as a way to escape Windows desktop lock-in and move to a webtop back in 1997. He would leverage Netscape's market share to put the Java VM on every desktop and in a sense deprecate the operating system to a commodity - Windows, Linux, SGI it wouldn't matter. It didn't quite happen on the client but it did bring server-side CGI into play. Even a weak webtop gave server-side LAMP hackers access to a desktop and the whole thing grew from there.
Andreessen is back with version 2 of Ning that is again a pitched as a platform - this time for Social Networks ( a rebranding of Ning 1 for social web applications). If you look at the Ning demo it makes it pretty simple to do a MySpace or Bebo clone in a couple of hours. They host it and for $20/month you can buy the right to remove their ads and display you own. The audience here is entrepreneurs comfortable with PHP/CSS hacking. Ning do all the "heavy lifting". Coupled with OpenId this space could be interesting.
Andreessen has been involved in three and a half startups according to the Scoble interview and apart from Ning he personally has made lots of money on all of them. It looks like he after spending $9M of his own cash he has turned myspace-like social networking platforms into a commodity. The trouble now is making money.
I think the trick for Ning will be to find communities that are compatible with the "casual friendship model" of Bebo and find these communities in their thousands. This may work given the size of the Internet audience. However, I don't think that lots of existing communities will migrate to a Ning-like platform as they will continue to do their main contact in person. The other problems is that all on-line services are adding social network elements as covered in GigaOM - Are Social Networks Just a Feature?
That Google succeeded where Netscape and others failed has been the big surprise to me. You could say Google is targeting existing social networks with their Google Apps for Groups. It's a variant of the Google Apps product and they haven't bet the company on it. They have delivered the platform that Netscape pitched in 1997. It will be even more complete with support for offline apps.
Netscape's ultimate product was its IPO as they, like most struggling companies, oversold and under-delivered to clients of their server-side products suite. They eventually gave up on the development of their platform, spun it off to Mozilla and joined AOL. I'm surprised Mark is still keen on platforms.
Ning may hit on something over time but it's a high risk to sink $9M your personal fortune into it. The Internet is a tough place to make money (honorably). This is especially true in the platform business but Mark has done okay before.