[bomdo]

Yes, if proven. If someone promises 1000 clicks for your dollar and delivers only 999, they are at fault, have not fulfilled the contract and either you should be reimbursed or they have to deliver the missing click.

That Facebook talk publicly about this issue (naming it a software bug) either means some lawyer business is already happening in the background, or the difference between what they promised and delivered is so obvious that it is just a question of time. This article is bad for Facebook's image as an advertisement platform and there is no reason to publish something like this, other than liability.

That said, Facebook has good lawyers and will obviously make it exceptionally hard for customers to prove Facebook is at fault. Additionally, their terms of service for the self-serve ads[1] is filled with blurry statements such as "we are not responsible for [...] technological issues [...] that may affect the cost of running ads", which will make legal battles lengthy and boring.

[1] https://www.facebook.com/legal/self_service_ads_terms