They are mounted RW because of recovery-mode options like dpkg "Repair broken packages" (actually an upgrade as per bug #452222). There is an fsck option that is invisible on Ubuntu 10.04 (Lucid Lynx) due to bug #566200. It creates a flag file, /forcefsck, that is checked for by the mountall.conf Upstart job to force a fsck at next boot. Creating the flag file probably is relatively safe as / gets checked before mounting.
They are mounted RW because of recovery-mode options like dpkg "Repair broken packages" (actually an upgrade as per bug #452222). There is an fsck option that is invisible on Ubuntu 10.04 (Lucid Lynx) due to bug #566200. It creates a flag file, /forcefsck, that is checked for by the mountall.conf Upstart job to force a fsck at next boot. Creating the flag file probably is relatively safe as / gets checked before mounting.