I used this in the past as well. But then started thinking about what non-critical is. As a "internet professional", even my Facebook account being compromised would be negative impact on my image; on LinkedIN doubly so due to it's professional character. So I basically decided that I'm not going to distinguish at all (sliding slope) and just have randomly generated passwords for all sites (not for my Mac though, too much hassle/attack vectors are different).

Safe >> Sorry

EDIT: Just checked, and my randomly generated password is in the leaked list of hashed passwords. I'm not using that same password anywhere else, so the source MUST be LinkedIN through whatever means (or it's some Mac/PC based attack vector, and these folks only leaked LinkedIN accounts which sounds very implausible).