While the Sidekick data _is_ HTML, and it will work fine served up by a web server, that wasn't the primary design goal.
The intent was to make it possible to carry your Yojimbo data with you _on_the_device_, and NOT require a connection to the network.
For iPhone and iPad users, I expected people to use FileMagnet, AirSharing, or something like that to sync the entire Sidekick folder on to the device. Then open the Index.html file (each app I looked at has a different gesture for this step)
Android users would mount the phone like a disk, then sync the files to the storage card, using ChronoSync, Unison, or something like that. A bookmark to content://com.android.htmlfileprovider/sdcard/Yojimbo/Index.html makes it easy to browse.
Windows users could sync the Sidekick data onto a USB thumb drive (using the same tools as Android), plug that into the computer, and open the Index.html file with Firefox, Safari, etc.
As far as using an actual webserver, I thought a company or organization could "publish" their office manual by using Yojimbo to create the pages, and hosting the Sidekick folder on a machine hidden behind a firewall, visible only to people at the office.
One thing I really wanted to work was Dropbox. I expected to be able to sync Sidekick to my _private_ Dropbox space, and once logged in, browse from anywhere. Due to some design choices at Dropbox, this is not currently possible, as HMTL pages loaded from the private area do not load CSS or Javascript resources. I believe our support people are working with them to find a resolution to this shortcoming.
In any case, those are some of the usage models we tried to build for. Notice that "turn on web sharing, configure Back to My Mac, and cross fingers" was not on the list. :-)
Steve