Google’s unofficial corporate motto is “Don’t Be Evil.” Unfortunately, that motto can actually get Google’s customers in trouble when it comes to accidentally deleted information. Here’s what Google’s new, unified privacy policy says they do when you delete content from any Google service:

“We aim to maintain our services in a manner that protects information from accidental or malicious destruction. Because of this, after you delete information from our services, we may not immediately delete residual copies from our active servers and may not remove information from our backup systems.”

In other words, just in case you didn’t mean to delete something, Google might keep it around for a while. Maybe.

In the specific case of Gmail, Google has gone on record that they keep a copy of your deleted messages around for 60 days. After that, they’re gone forever (setting aside the necessary legal caveats).

In simple terms, this is Google not being evil, as they don’t keep your data around after you tell them to get rid of it. There is no after-the-fact data mining or ad targeting. When you say something needs to go away, it’s gone. The 60-day holdover period is there only as a necessary legal defense. If you’re, say, destroying evidence by purging your Gmail account, and someone serves Google a court order to produce your deleted Gmail messages, Google needs some recourse, at least in the reasonable near term.

In practicality, what you delete from Gmail or Google Docs or YouTube is gone. Even the stuff you accidentally delete. Even the stuff that a hacker deletes after they steal your password. Even the stuff your dodgy smartphone app accidentally deletes when you sync it to your Google Calendar. When it comes to Google, “delete forever” actually means delete forever.

Yes, Google keeps backup copies on their servers for a month or two, but that’s for Google’s benefit, not yours. You have no obvious mechanism of asking Google to un-delete something. By respecting your privacy, Google has given you no margin for error when it comes to accidental deletion.

Roughly one-third of all data loss is due to user error, and that’s exactly the kind of lost data Google’s “Don’t Be Evil” mantra can’t help you with. That’s probably why, when it comes to Google’s business service, Google Apps, user error is responsible for two-thirds of all lost data. Google has solved most of the hardware problems and software issues that can spontaneously delete data; but hardware and software can’t protect you from yourself.

If you don’t keep anything irreplaceable in Google services, you have nothing to worry about. But then, no one thinks their data is irreplaceable until the wedding photos stored in Picasa or the college journals published on Blogger suddenly disappear.

Luckily, there are techniques and services out there that can keep backup copies of your Google data. Google Takeout is Google’s own service for downloading your online data. Gmail and Google Docs both have offline modes that can store local copies of your emails and documents. Backupify (for whom I work) offers automatic third-party backup of several Google services, including Gmail, Google Docs, Picasa and Blogger.

Bottom line: if you rely on Google services, you can’t rely on Google to keep indefinite copies of the data you accidentally delete. Doing so would be “evil” — and that’s not in Google’s business plan. It’s up to you to keep backup copies of your Google data. After all, only you can protect your Google data from its greatest threat — yourself.