This is a nuisance rather than a major problem when the intended source is an application running on your computer, because you can always restore the most recent backup. You do back up important data at least once a day, don't you?
But it's trickier when your primary data is stored in the cloud.
Google has addressed this issue in Google Contacts by adding a 'restore' feature that allows recovery to any point in the previous 30 days.
If you do make a serious mistake that would be time-consuming to unscramble manually, the Restore contacts command in the More actions menu lets you recover to an earlier version. Among the choices are 10 minutes ago, yesterday, and a custom setting that lets you specify the numbers of days, hours and minutes that you want to rewind.
That last option doesn't sound very convenient - wouldn't it be more natural to be able to enter the date and time that you want to restore from?