In theory, Facebook's (and Google AdWords') auction model protects you against this. In theory, you're tracking conversions/effectiveness, and if the number of

In theory, Facebook's (and Google AdWords') auction model protects you against this. In theory, you're tracking conversions/effectiveness, and if the number of bots that click your ad double, that means the ads are worth half, so you adjust your bid accordingly. That's the theory at least. Reality is probably different.