Having seen a tort liability suit all the way through trial and just generally having WAY too much experience with lawyers, I will offer the following 1000 cents.
Flying with a friend leads to potential tort liability. Allegations of tort liability generally revolve around the following concepts:
- duty of care (your general duties to minimize the threat or occurrence of harm to another)
- negligence (your failure to perform duty of care leading to damages)
- Case law and other common law concepts that generally demonstrate how your actions or inactions deviated from that of a "reasonable" person, allowing points one and two to occur
If you fail to perform obvious duties of care (basically, you're a dumb*****) no release of liability in the world is going to protect you.
If you generally act like a reasonable person while flying, you're mostly covered. But what is a reasonable person, exactly? It's the actions of an average pilot of similar training and experience to yourself. That's it. However, there's a big hole here: your passenger might not be aware of the risks associated with flying with an average responsible pilot of your skill level and training.
That's what your waiver does. It explains to the passenger that there are clear risks involved, and that they could die from this activity. It lays out your very basic training credentials, flight hours of experience, approximate engine hours, etc; indisputable, easily discovered facts. It points out general accident stats associated with pilots of your skill level. It points out a few of the statistically most probable worst case scenarios for same. It does NOT contain subjective self assessments or observations about the specific airplane you are flying. It explains that you have explained all of the same to the passenger, verbally. You want a waiver so that if something bad goes down, there is no way anyone can say "It's his fault, he didn't tell me the risks!"
Get that waiver, don't be an idiot, and have at least $50,000 available for a really good attorney because they still sue anyway and they need to be shown how they have no case; that's about as good as you're gonna get.
Disclaimer: I'm a brand new member, I have no pilots license, and this is not legal advice because I'm not a lawyer.