Validation is the first line of defense against injection, cross-site scripting, and many other attacks. Omitting it in modern web applications is simply negligent.
When creating a Struts ``++ActionForm++``, you have the choice of extending something from the ``++org.apache.struts.action++`` package, or extending something from the ``++org.apache.struts.validator++`` package. Since you can't use the Struts validator capabilities without extending something from the ``++validator++`` package, that should always be your choice.