It might be difficult to catch depending on the how macro attributions they could make on you, depending on the time scale - say over 20 years, if you cleared the history every year, it might give them insights that might be hard to correlate to earlier history.
If there were strong whistle-blower laws and pre-set rewards however, then might get a whistle-blower who could earn themselves say $1B+ (based on size/revenues of Facebook) for outing the deceit - which then Facebook would be fined for.
Is a scandal a huge issue? Despite the recent #DeleteFacebook and everything, Facebook wasn't really impacted all that much and is still making tons of profit even without the 1% of users who did delete it. A future hypothetical scandal where another 1% deletes it would be worth it considering all the data and revenue they made from abusing people's data before the scandal.
