Will people never learn? Do you realize what happens when your password manager itself gets compromised?
Using a password manager is trading security for conveniency. This is simply not acceptable.
I fully expect all the people using insecure security practice and all the people selling snake oil to downvote this.
The problem, however, is that you can't argue with facts. And the fact is that trading security for conveniency is a very stupid thing to do.
Also, note that if my password manager is compromised, it means that the attacker has some level of access to my machine, since that is where my passwords are stored. In that case it is reasonably likely the attacker can also install a keylogger. This will reveal my often-used passwords even if I do not use a password manager.
For example, if you're password is "puppy" and you're signing-up for HN, your password would be:
pHuApCpKy
And, if you wanted to make it stronger, salt it with some special characters.
p~Hu!Ap@Cp#Ky$
... which is just the shift-characters on a number row in order.
This way, you only have to remember one password, and it is service specific, and pretty strong. No password manager needed.
Of course, I don't do this. I use a 1Password and KeepassX.
To be honest, firefox has an encrypted database of site-passwords. What's wrong with that?