We detected the following sites were using Wikispaces
If a CMS doesn't have meta tags, it will often have other uniquely identifiable html markup. This can range from unique html comments, ids or classes.
Similar to identifiable html markup, a CMS will sometimes insert unique Javascript code into web pages.
Some content management systems also offer hosting. A website hosted on a CMS developer's domain is a dead giveaway.
Dedicated Content Management System Detection