Since to this point you speak no knowledge of actually running ads on any of these Networks, you may not know that ads get approved all the time only to be later disapproved for not meeting their advertiser policies. I have run ads on almost all networks that have been approved and then a day, week or even a month later been disapproved. Just because you see an ad running does not mean it meets the advertising networks policies. Many times the ads are automatically approved at first and then a secondary review is given later to make sure it meets guidelines.
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