There are still so many people charging for reviews and endorsements and sponsored posts without properly complying with the FTC's 16 CFR 255 Truth in Advertising disclosure requirements.
Here is a Presari shared search on FTC requirements and social media marketing
At Google and Bing, use the time tools to search for the warning letters sent to endorsers and celebrities who were found to violate the requirements.
You can see the letters themselves here:
Education letters (sent to 90 influencers)
Warning Letters (sent to 21 endorsers)
In June 2018, the FTC closed down an Internet Business Coaching operation
If you are going to conduct a social media marketing campaign, you might want to take a close look aty this November 2018 FTC notice describing the actions taken against two US Olympic athletes.
Here is a really clear and precise statement of the do's and don't for social media influencers.
Here is a link to the latest FTC Guidance describing how to properly conduct regular and online advertising, marketing, endorsements, and book and product reviews.
Do it right. Clear and conspicuous. Above the fold. First and not last. Large and not small.