There seems to be a bug (maybe intentional) in the fuse package.

In debian proper any user can mount a fuse filesystem (that is the point of fuse after all) if they are a member of the group "fuse".

There is a udev rule (/etc/udev/rules.d/91-permissions.rules) that tries to set the group ownership of /dev/fuse to "fuse", but fails (presumably) because the group doesn't exist.

To be able to mount sshfs as a user you can either (all must be done as root)

a) chown root:users /dev/fuse (which doesn't persist after a reboot)

b) edit the line in 91-permissions.rules so that it references the "users" group rather than "fuse" (wot I done).

c) add the fuse group and add "user" to it.

The best solution is probably d) add the "fuse" group when the fuse package is installed.

I'll try and find out how I report that bug as I'm a bit new to the N900/maemo.