In a panel entitled "Second Life as a Platform" held during the Life 2.0 convention this week (see Metaversed coverage here), a panel that included folks from Linden Lab, Amazon Web Services and the Lib Second Life project agreed that scale and reliability were the virtual worlds greatest challenges.
Amidst loose talk of Second Life expanding web services, and the coming opening up of the Linden server code to the open source community, the overriding issues of scale and reliability were forefront. Amazon's Jeff Barr said that he (they) were actively engaging with the SL community because developers inworld were at the absolute cutting edge. They're prepared to accept a certain amount of instability as price for being at the leading edge of the 3D frontier. Amen to that, there's no shortage of awesome talent in Second Life, that's for sure.

Amazon's Jeff Barr, aka Jeffronius Batra at the Second Life as a Platform Panel (more images here)
When asked what the greatest challenge for Second Life this year was though, every one of the panelists agreed that scale and reliability were of greatest issue. With resident complaints becoming very public, it would seem that some upcoming features such as voice integration may be overshadowed by stability issues.
Only time will tell.