Should I allow my employees to participate as themselves on our social media sites?

Jeff,

Your employees are already the face of your company in offline capacities - customer service, sales, reception, etc. They have deep knowledge about your company, services and products. For example, Zappos (though a B2C example) is successful in part due to its employee participation on social networks.

Whether or not to have your employees participate depends on part of your corporate culture. Assuming that you have a very open culture based on your questions, my recommendation is to draft a guideline of acceptable online behavior for employees. By crafting a positive guideline vs one that highlights don'ts, I believe, will allow your employees to move forward on a positive note. Once your guideline is completed, have a training session with employees to answer questions and provide an open/transparent environment. Finally, I recommend creating a format to identify employees online, such as NameAtCompany.