Private browsing isn't going to help with sites that publish their databases in plaintext, as in the link.
Otherwise a password-not-yet-leaked will no longer be. If you didn't turn on private browsing as I suggested and are using Safari, type the password you searched for in your URL bar now and you will see why I said what I said.
And for that matter, why do you have so few that you can easily google for them instead of generating random ones per site?
(Fun fact, googling for your e-mail address reveals a hash of your password on MtGox.)
For that matter, I have a unique password (with the necessary special characters) for each account that associates with my identity (Not naming any examples here), but only several unique passwords for websites I don't intend to use much e.g. to read newspapers, and apparently, MtGox.
(Yes, I was searching for my MtGox. password because it was the same password I used for random throwaway sites. No I never used it, I don't even remember having confirmed my account there. My asset in bitcoins amount to < $2 USD.)
I still don't understand why all the downvotes. It would've helped me if someone reminded me not to actually google my password with my browser watching. Apparently not anyone else.
EDIT: I, however, do not agree that it is necessary, even more being a link posted on HN