
Plenty of people delete their Facebook accounts in a fit of rage or the spur of the moment. Luckily for them, the regular way of doing this doesn't actually delete the account, it just "removes" or "disables" it.
This means that the profile won't be visible or searchable, but all of the content will be kept by Facebook and some of the content, shared with friends, may still be visible to other users.
When users decide they didn't actually want to delete their accounts, they can simply restore their profiles and be done with it.
"In case you want to come back to Facebook at some point, we save your profile (timeline) information (friends, photos, interests, etc.) so that the information on your profile (timeline) will be there...