I generally use the same password for what I feel are non-critical sites like LinkedIn, twitter and Facebook. Another password for testing new services/apps etc. As a rule any site that may contain my credit card data or sensitive information I use a separate password. I feel this is the best compromise to having complex passwords for each account.
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).
