I have been doing a lot of reading about social media sites and their terms of service. Most of them have a clause that states that you agree to give them, at no cost to them, a license to use any image that you place on their site without any restrictions. This means that they can sell your image to any company or person to use in any way they wish.
For artists, especially photographers, this is a very bad because it could affect your income as well as your business image. Think for a minute about a lot of the advertisements that appear on the internet and in spam email. When you post an image to a social media site, you give them the right to sell your image to any advertiser. How will you feel when you see a photograph of yourself or a family member being used to promote pornography or other industries or products that you do not support.
The options that are available are limited. First, the artist could close their accounts on these sites, which is not a practical option since a lot of artists connect with clients through these sites. Second, the artist could stop posting images on these sites with similar problems to option one. Third, an artist can have a blog or other site to post photographs to and link those to the social media site, with a lower number of people seeing the work. Use of the free image hosting sites is not a good option here, they have similar clauses in their terms of service. It is getting to the point that artists have to be willing to pay to protect their rights to their own work.
The options above do nothing about photographs already on social media sites, the license has already been granted and is irrevocable. They have copies of the image and can use it how they see fit.
Since social media has become an integral part of the art world artists need to figure out how much of their art are they willing to give away to social media sites to promote themselves. This is now a cost of doing business in the art world and many artists do not realize it yet.
As an artist, I am evaluating the worth of social media in promoting my work and just how much of it I am willing to give away. For social media to be most effective, I should post my best work; however, I should not be giving my best work away. If I post lesser works, the public will assume that it is my best work and not understand that I produce better work that they will have to see in person.
This is not an issue that one answer will work for all artists, the decision will be as personal as their art.