The old saying to remind yourself not to do something stupid, or at least not to write it down, was once “If you don’t want to read it on the front page of the newspaper, don’t do it.” That has changed.

The Sony Hack provides the latest evidence that inquisitive news reporters aren’t the most likely threat to the privacy of your business decision-making. Most of us have been treating email as private correspondence, including everything from snarky comments to credit card numbers in the messages we send across the Internet in the naïve belief that no one would be looking in.

While you can reasonably assume you won’t be the victim of anything as disastrous as the hack against Sony, the case provides a lesson for all of us. Don’t assume that what you write in an email will remain between you and the intended recipient. And if it does become public or at the least known to people you didn’t want to see it, resolve to take the only reasonable action: apologize.

Do it quickly and sincerely. Send your apology to everyone you know to be insulted or affected, as well as everyone on the sidelines. Assume everyone you know will want to hear from you.

In the meantime, remember that things you can get away with saying face-to-face to friends and even enemies do not translate the same way in writing.