I've done a lot of googling but I have come up short; what is the purpose of the sambashare group? From what I can find, it appears to be a Debian only thing. The only concrete information I can find is from this Ubuntu page:
Share files with the local network
This right is gained by adding the user to the "sambashare" group.
The "sambashare" group can access the /var/lib/samba/usershares directory.
I see it suggested quite a bit as a fix for sharing issues to add users to this group, but from the above it seems like this group is just for creating shares? I created a user yesterday and it works fine under the normal Users group.