You may be right that many companies behave this way, but they at least pretend that they don't. The companies I've worked for have always been extremely conscientious about honoring data-related terms, even if no user would ever know. The fear of getting sued is strong.
In any case: when I say that Avid Life is nowhere near the bottom quartile for companies when it comes to security, you can take that to the bank. Or, don't, if you're worried about taking things to places that won't lose your data in a breach. I guess you can take your data to Facebook in that case.
Given backups and billing records and stored message histories and so on, its not really a question of 'deleting an account'. More like 'making an account no longer visible/available to the current interface'. Nobody thought they'd wipe any disks or anything, in anticipation of a big data breach, right?
It'd be hard to argue that it conduct that disregarded human life, though.