Ockham's Razor: "Pluralitas non est ponenda sine neccesitate'', which translates as "entities should not be multiplied unnecessarily''.

Hanlon's Razor: "Never attribute to malice that which can be adequately explained by stupidity''.

Mooers' Law: "An information retrieval system will tend not to be used whenever it is more painful and troublesome for a customer to have information than for him not to have it." (http://www.tracfoundation.org/mooers/infosci/mooerslaw.htm)