Firstly, there's several HUGE issues everyone selling these services needs to think about.
Firstly, Company Image. Are you going to be known for selling 'Facebook Likes' that aren't genuine, drop & are poorly made, if your answer is no, you need to think about the places your buying from.
Secondly, Customer Issues. No customer likes 'Facebook Fans/Likes' Drop full stop. If they are fake, and they drop you have absolutely 0 excuses. However real genuine people make there own choices and you cannot be held accountable for what they do, it is down to the customer to engage with his target audience and expand from what you have provided.
Sooner or later everyone will know that fake 'likes/fans' are useless. Less & Less people are using these services for the sheer fact they do absolutely nothing.