In Lubuntu 12.10 Beta1 (fresh install):
PCManFM requires a password to mount partitions. This is very inconvenient as many people place files on separate data partition.
This should be an easy fix. I think it is a setting in /usr/share/polkit-1.
I also filed this on launchpad under Pcmanfm, but not sure if it was proper place.
lstranger: Many hanks for addressing all bug backlog for Pcmanfm. I was giving up hope about Pcmanfm and Lubuntu.