Vanilla is a product of Lussumo:
Documentation and Support.
The way you guys speak of it the most fun thing about Second Life was the equivalent to the 'Mods' for games like Half-Life. Why bother integrating a whole world together when people are try to create completely different 'islands'? Sure, it's ideal, but the system requirements to keep up with even the basic underpinnings of the whole 'world' are outstanding. It didn't seem they had a good plan for growth.
Maybe if they used something like the World of Warcraft engine, implementing better more intuitive creation tools(I hated the tools, honestly) they'd have a winner on their hands...