Amazon's continued roll out of large scale grid services now also has a database. It's less interesting than it ought to have been: They haven't done unlimited scale through parallelization, but scalability in terms of number of clients accessing the server is there. What I would consider interesting, though, would have been the ability to story very large tables and query those. Since you can't do any joins it seems a pretty naive implementaiton of that would work out.
Plus points for extreme simplicity - it's a basic object/attribute store with robust but simple search functionality on top.
My previous job was a at a domain registrar - where we ran something that looks a lot like a domain registry. This would have been perfect for that kind of application.