As long as I'm blogging about filestreams…
Folks always want to know if the filestream information can be stored on a remote share. They look kind of disappointed when they hear that the filestream filegroup must exist on a local (to the SQL Server instance) drive. However… (isn't there always a however?)
For SQL Server 2008, the SQL Server team released a companion feature to filestream called remote blob storage (RBS). RBS consists of a set a stored procedures and an SDK that allows you to store your blob on a remote blob store. The SDK works differently than the filestream storage feature. And, to use the feature, you need a RBS blob store provider. Looking around, EMC2 has an RBS provider for the Centera product line. And there's a sample provider and code to use it up on CodePlex.
The SQL Server team released the first version of RBS as part of the SQL Server 2008 Feature Pack.
They'd always said they'd be bridging the gap between filestream storage and RBS in future. We'll…the future is soon (or now, depending on how much you like CTPs). The November CTP of the SQL Server 2008 R2 Feature Pack comes with an RBS provider for Filestream. You still have to use the RBS APIs, but you can have your (filestream) cake and eat it too. Remoting. There's little info right now, but there are a number of postings on the RBS team's blog. Including a comparison of filestream storage and RBS. In addition, RBS & filestream appears to hook into SharePoint 2010, but I'll leave the description of that to the SharePoint 2010 documentation (which has just been updated today).
And, BTW, if you were going to ask "Are features that appear in the SQL Server Feature Packs supported?", the answer is yes. I asked.