I'm also one of those that has classes of passwords - I have 4.
Don't care about.
Could cause an annoyance if hacked, but not the end of the world.
Shopping / Social Networking type sites
Ultra Secure - this must not get hacked type sites.
I will however point out I have been a victim of identity fraud - despite being the kind of person who shreds receipts and letters :/ I was rather shocked to receive an Argos card through the door followed by a JJB sports card - I phoned both companies and was informed that I had signed up for both cards in a retail park some 600 miles away. CIFAS (or however you spell it - sounds like sy fas) got involved - and any further attempts to open accounts in my name would result in me getting a phone call to confirm it really is me.
Now - the surprising thing was the way it works - you seriously would not believe how easy it is.
Having recently been registered with companies house as a director of a business - they got my details from the publicly available data (which they pay for) which companies house publish online. Next because they had an existing credit or debit card with the same initial and surname as me - they went on a shopping spree to specific shops - this is where the situation gets stupid.....
They go into Argos - purchase £500 worth of items, when they go to pay - Argos say "if you take out an Argos store card - we can transfer the balance of this transaction to the card" so they get a card using my details, they have a credit/debit card that has the same details as me as proof. The transaction gets transferred to the card that doesn't even physically exist yet and that they will never see. They walk out of the shop with their items and haven't paid a penny for them. Next they go into JJB and repeat the process etc.
Moral of the story - even if you have ultra ultra secure completely uncrackable passwords - the gov publishes enough information about you online that if someone wants to steal your identify - they can.