Typically, employers use non-compete clauses to prevent former employees from competing with them after they’ve provided them with trade secrets, customer information, or other proprietary information. Non-solicits can essentially have the same effect – by restricting or preventing a former employee from calling on or contacting former customers. Here is an example:

You hereby agree and covenant that during your employment with XYZ Company, and for a period of one year thereafter, you shall not . . . : (1) encourage the customers of XYZ company to refrain from doing business with XYZ Company; (2) solicit the business or accounts of the XYZ Company’s customers; and (3) introduce by telephone, email, or any other method: (i) any sales representative that is employed by or otherwise affiliated with you; or (ii) any subsequent employer you may have …

Former employees can conceivably use social media sites like LinkedIn and Facebook to reach out to former customers. In the TLK Networks case, a former employer sued former employees over a non-compete and used LinkedIn communications as evidence. 

 Through "updates" and "tweets" individuals can reach out to possibly hundreds of individuals with a short message. Something like "Anyone aware of an individual who might be interested in a position with [insert name of company] doing xyz?" or "Anyone have any leads for someone who might be interested in purchasing [xyz product] for [xyz price]?

Though the solicitation is not directed at any particular individual what if former customers or clients who might be interested in the job or product could follow up on the communication? While we tend to think of solicitations as a phone call or letter, social networks blur what is really a solicitation.

A non-solicit could be drafted that could address this communication and specifically prohibit it. The employer could define an improper solicitation "to include any type of communication, including but not limited to, status updates, tweets, etc. on any type of social network to include but not be limited to LinkedIn, Facebook Twitter, etc."  Employers need to review their agreements to make sure they address ever evolving communications tools like social media.