Thanks for all of the comments. I will try to address/answer some of them below:

Lawson: Concurrency is also faltering. I remember early last year Linden's CTO predicted Second Life would reach 150,000 concurrent users by year's end, and it didn't happen. Regarding your comments about Linden's response to bugs and getting feedback from the community, I tip my hat to them for taking this attitude but would also like to note there are still many, many people who are disappointed with the pace of improvements and the system for vetting suggestions. Linden's stated support for standards is wonderful, but it's still not possible to transfer objects and avatars between worlds.

Prokofy: We are on the same page when it comes to competition, but I respectfully disagree with your statement, "it seems unlikely they will achieve very quickly the same complexity and density of capacity and features." The history of computing technology is littered with examples of former high-flying companies with super product lines being knocked off their pedestals by upstarts or more capable competitors in an extremely short period of time. This is such a relatively new field that examples are hard to come by, but in the computer graphics domain, SGI and id software are two trailblazers that were dethroned in this manner.