i predicted this years ago when my last company first thought of migrating to a 3rd party to host their mail cheaper. i don't remember if they ever implemented a strategy to back up the mail remotely, though i do remember for a while the "beta testers" had their mail sent both to exchange and gmail.
point is: don't tell me just because a company is large or reputable that the basic procedures of any IT department should be ignored. if you have data and it's important you need to keep a backup, and you need to be able to verify the backup. if you can't put your hands to a redundant offsite copy of your data it's going to vanish eventually.
to all the people that lost their mail: i feel for you. i've lost data before too because i didn't back it up. however, we do learn that most of our correspondence's history is unnecessary. nice to have "in case of emergencies", but unnecessary. do i really need those mailing list threads from 3 years ago? will that website confirmation really be necessary down the road? nah. the personal messages passed between family and friends may be missed, but i've never really "gone down memory lane" before and doubt i would in the future.
this is also the risk you take when you rely on web-only email. luckily i believe gmail allows any user to make an offline copy of their mail, but some services like yahoo and hotmail do not (unless you pay). i'd like to see a push for competing providers to mirror other providers' datasets for redundancy but that might just make them less important in the end.