A wonderful summary by Wayne Porter attempts to predict the use of different virtual world platforms, focusing on Metaplace, VastPark and Second Life.
To wit:
Second Life
I believe the struggles with Second Life have been based around its hyper-freedom. You cannot fit square pegs into round holes. This does not mean it does not have value, only that its value is misunderstood or misused….it will continue to serve niche and fringe markets and attract hyper creatives. I think new worlds or platforms like VastPark will fill the gaps that Second Life cannot due to the nature of the platform.
VastPark
From what I gather reading their blog VastPark posits a virtual world can be thought of as a collaborative wiki hence virtual world is controlled like a distributed content management system (CMS)
And, of course, all eyes on the big prize…Metaplace
It’s a nice summary, but misses a huge swath of synthetic worlds, not to mention virtual worlds that include elements of games. Ignoring HiPiHi is like the US ignoring China, but there are other worlds with different functions as well. Some of them are glorified chat, and some of them are 3D versions of Web pages. Kaneva, Twinity, There.com, VLES.com….examples of worlds in which commerce and content have different advantages in their expression.
And all of this ignores a move by Google, whose recent move into the Wikipedia space is an intriguing and explosive follow-up to its entry into social networking and wireless.
But all support Wayne’s basic argument that:
No one really knows, but no doubt MMOs, virtual worlds, 3D environments and rapid content creation tools for gaming environments are poised to explode. There will be no one “killer world or platform” but diverse companies that are honed to fill the needs of certain environments e.g. workspace collaboration, game play, teaching and education, and simulation.
Ultimately what I am looking at is how the traditional Web and 3D space will collide and what kind of real world fragments will be thrown off as this happens.
[...] To that I proffer that the future might not be “professionally made games”. That people will turn to platforms that allow them to make games and games will go independant. Just as we have now have micro content boiling all over the video and audio realms courtesy of YouTube and podcasts, we may, no we will probably, see the same in the games industry. Dusan Writer, who owns a company that does work in advertising, strategy, marketing and design working mainly in healthcare, environmental issues, and training noted my outlook on VastPark, MetaPlace and Second Life in a blog entry. [...]
I’m having a hard time using Vastparks Create tool!
Just shows that I’m no 3D modeller. 
VastPark’s tool is clunky, Kabalyero – and why they mapped the keyboard the way they did I have no idea. Having said that, I’ve been having fun playing with it and pretending it’s like the first days of SL.