scarier still is when they let you set it but fail to let you log in (generally happens more with length). i don't know what you're doing, but i know it's not right and it scares the hell out of me
I had that happen because of length at an online service we needed to use in high school. I believe my password had 9 characters. After requesting a password reset and experimenting I found that the registration form would allow you to enter a password of any length, but the login form would only accept up to 8 characters. What really shocked me was that I was the only one of my classmates that used a password longer than 8 characters.
Some places have been known to just truncate the password...
I see this all the time. They accept it and then when you go to log in, it fails. I usually try chopping it down to 32, 30, 24, 20, ... until I hit a match.
I've had that happen with Comcast. I think they fixed it but it was pretty annoying. The signup password input had no max length but the login form did.