Facebook Advertisers now have the ability to promote unpublished as "Dark Post". As far as I know it's totally safe and the best way for now to advertise through Facebook as there is not risk of Ban Profile/Page due to over promotion. But, Have any negative effect of Facebook Dark Post??
"now"? that has been around for ages and is used probably by every page which advertises. At it's core it is a posting which will not appear on the page itself and you have to pay for it to be shown to people. Depending on the purpose of what you want to do you have post - and let organic reach play post and pay - organic plus visibility and can additionally appear with normal page fans due to engagement dark post - can have engagement but will only be shown to people when paid (of through notification if somebody f.e. had commented and now gets an update) Depending on what you are doing, it can be best to start with a normal posting and later push it when it runs well. Dark post are mostly for bigger companies, which also use the bulk upload to create.