The main reason why facebook and many other websites do this is risk minimalization. What if some spam filter goes wild and deletes half of all profiles? EDIT:

The main reason why facebook and many other websites do this is risk minimalization. What if some spam filter goes wild and deletes half of all profiles? EDIT: That was just meant to be an example. I believe it's generally a good practice to use a delete flag as the default option (unless there are legal or serious privacy concerns), because it makes you sleep better at night. I don't know if it justified in this case, but I just wanted to point out that they did not do it just out of pure evilness.