@Pam1291, a real security deposit is my number one complaint and concern. At any moment, any of us can suffer financial damage from a careless guest or even one who just has an accident, which can happen to anyone.
What a joke that Airbnb sent you a check for $50. In my interaction with many of the CS reps, I feel they are undertrained and probably underpaid - I would imagine many of them are young and don't own a home, so really have no idea what it is like to worry about the possibility of damage.
I have twice asked for money from guests - once for a broken flue on my woodstove and once for excessive cleaning (the guest didn't know that that had not been something we can collect on). Luckily, they both agreed and paid-up quickly, but if there was some really costly damage, it would be a real pain if they refused and simply closed their account, which I've heard of people doing.