I understand that the site does not force you to choose a strong password. I have ignored it's advice and used one of my usual ones. However, the first time I chose a password for the site, I thought it was requiring me to make a strong one. The interface is misleading in that way. So I chose a strong one and subsequently forgot it, requiring a reset which was a hassle.
I also understand that it may be seen as a good opportunity to teach people about strong passwords and encourage them to start using them. I think it would be fine to have a box on the sign-up page that gives information. But to have a box telling you "Your password is too weak" when you are choosing it is going too far.
Check this (pdf):
ABSTRACT: We find that traditional password advice given to users is somewhat dated. Strong passwords do nothing to protect online users from password stealing attacks such as phishing and keylogging, and yet they place considerable burden on users. Passwords that are too weak of course invite brute-force attacks. However, we find that relatively weak passwords, about 20 bits or so, are sufficient to make brute-force attacks on a single account unrealistic so long as a "three strikes" type rule is in place. Above that minimum it appears that increasing password strength does little to address any real threat If a larger credential space is needed it appears better to increase the strength of the user ID's rather than the passwords. For large institutions this is just as effective in deterring bulk guessing attacks and is a great deal better for users. For small institutions there appears little reason to require strong passwords for online accounts.
By all means give information about password strength, and why choosing a strong one may be good. But let's avoid discouraging people from using weak ones if they want. It is not a if the forest is a major hacking target.