Lock-free databases

Is there any significant benefit to making a database lock-free? By lock-free I mean the internal implementation. I know there's a database out there that frequently claims to be lock-free but I've looked at their "lock-free" patents and I think most of the benefit in their case is from being an in memory database. I'm talking about real lock-free, e.g. making the indices lock-free to allow concurrent updates without having to rebuild the indices, or allowing queries to run concurrently with updates.

In the case of an in memory database, you could put the database in to a read only shared segment and allow processes running on the same machine to run queries directly against the memory without any IPC or communication overhead. No syscalls essentially.

And if there's any benefit to making a database lock-free, would there be a particular type of database that would benefit the most? Or is lock-free only suitable as a marketing term?  

-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.