Sorry, but that's incorrect.
Waivers are valid legal instruments provided that they meet certain conditions. Similar to contracts in that respect.
TallAdam, have a look at at the legal concepts of assumption of risk and volenti non fit injuria, and do a little reading about tort law. Here's a good example of an implicit waiver of legal recourse: you go to a major league baseball game and get injured by a hard-hit foul ball. It's highly unlikely that you will have recourse to any legal remedy against the stadium or the teams, although they may agree to pay for your medical treatment as a business practice.
If you want to create a waiver that will stand up in court, consult with a licensed attorney in your state and discuss your situation in detail. Why not use google, there must be plenty of boilerplate waivers available free on the internet.