First full disclosure - I work for xkoto Inc. as Chief Strategy Officer. Regarding scale-out, if you visit http://www.xkoto.com, you can get the low down on how our GRIDSCALE software can scale-out workloads - of course mileage varies with the workload - but with 80/20 read/write splits we have shown over 85% scale across multiple shared-nothing active-active databases. GRIDSCALE also provides continuous availability, keeping data consistent across databases. We are in limited beta now on SQL Server and are targeting mid 2008 for shipping.