There are many factors that could affect your decision to post your work on one of these "academic social network" sites. This presentation by Andree Rathemacher & Julia Lovett, University of Rhode Island, is a great resource on this topic.
The highlights are below:
If you still wish to be a member of one of these communities, you have the option to link to the DigitalCommons record for your work. That would ensure all users of all sites are presented with the approved version of your work and the usage of your work would be tracked in the Author Dashboard.