The longer, the higher security.
I have a 15 characters long password to generally use and prevent me to send and check email to find or remake password.
As security issue is getting bigger, generally sites ask people to have longer password. but I don't get why Opera ask people to have less longer than 12 letters long one.
Actually I didn't have any trouble with security issue yet, but just it's bother that I have to make and remember another version of password. however if someone secretive with security issue, I guess this is quite a big deal.
I hope Opera allow me to have longer password.