SMB is really interesting idea, I may be miss understanding it, but would that in theory enable us to browse a remote SMB directory from within a SilverStripe site? If so that opens up a wide range of possibilities in terms of Intranet applications, for example if a company wanted open up part of their file server as as part of an extranet (which we've had a number of requests for in the past).
It also brings up the bigger issue of other "file systems" - for example, some video based content which we stream for clients, we host on [url=http://citylink.co.nz/services/streamingnet.html] Streaming net [/url], a mini Alkami service, other clients with lots of big files may want to host those files on the [url=http://www.amazon.com/gp/browse.html?node=16427261]Amazon S3[/url] service as the bandwidth and storage is cheaper than what can be offered by most web hosts.
So, in the future I'm guessing we'll need to deal with a number of "files" areas, beyond "files on your webserver"..
...another file based authentication protocol to think about is [url=http://www.webdav.org/]WebDAV[/url].
Anyway, really excited by your work :-)