There is an issue reported in Polish Wikipedia (permalink): users (mostly IPs) are sometimes making unintentional reverts by editing patrolled versions of a page, when there is at least one version waiting to be patrolled. Examples:

• IP wanted to make this edit, but instead made this (because there were two not patrolled edits).
• IP wanted to make this edit, but made this (because there was one edit waiting to be patrolled).

Users get information about the fact that they are editing older version of a page, but (1) most of them don't know the difference between 'older', 'current' etc versions and (2) they get a huge mass of text (honestly, I'm not surprised that these informations are usually ignored).

There is a proposition that users (IPs mostly) should always edit the newest versions (i.e. by clicking edit/edit code they should always edit the newest version [even unpatrolled] and not the last patrolled version; even if they are not aware that there are different versions) and editing older versions should be possible for them only via 'history' tab.