Up to some time in past the GNOME have rather... impressive... amount of customization regarding the keyboard (intimidating would also be a correct word). This was removed as of GNOME 3.x, which is a good thing.

Quick search over the live.gnome.org show that the problem was noticed back in 2005 during first GUADEC usability hackfest[1]: "Ubuntu supports the annoying and near-useless Insert and Caps Lock keys, with no obvious way to deactivate them. (Windows and Mac OS also make the mistake of supporting Caps Lock. I mention it here because Ubuntu — unlike Windows or Mac OS — offers no fewer than five options for “CapsLock [sic] key behavior”, but none of them are “Off”.) (mpt)" - ironically it was not an option in Gnome as well (or at least clearly marked).
Quick Googling is showing vast amount of tips how to notify the user that they have caps lock on.

Ironically it seems to be an easily-pressed very uncommonly used key. In my totally unrepresentative survey I have noticed that 1 person is using it at all (power users) while all others (both normal and power users) used it "only by accident". 

Would it be possible to have an option to render caps lock harmless (for example change it to shift key or disable it)? It is not a request for 10 options or anything like that - just one to disable a key which have low usability

[1] https://wiki.gnome.org/Stuttgart2005/Hackfest?highlight=%28caps%29%7C%28lock%29
[2] http://blog.gerv.net/2009/07/gnome_usability_progress/