You can't put a price tag on individual users, thus it might be hard to determine when a user causes Facebook to suffer a loss just for hosting their content. See it like this: If a user blocks all advertisement, he still interacts with his friends - which is hard to value.
On the other hand - if you create an account, upload a few photo albums and don't add any friends to your account, you will probably cause a loss ;)
On the other hand - if you create an account, upload a few photo albums and don't add any friends to your account, you will probably cause a loss ;)