I had a very insecure password on adobe.com. i.e. low-enough entropy that 55 users had the exact same password. I figured since Adobe do not have my credit card number and there is nothing to gain by impersonating me on that site, it did not matter. I have not used the same email/password combination elsewhere, but even if I did it would only be on other low-value accounts. I'm not worried about attackers finding it by association either (they will have it already from dictionary attacks.)