Broker's get hit with "failure to supervise" in most cases that are brought against them. This is not any different, he's a registered rep/broker dealer. FINRA still has regulations surrounding social media usage.
“Investors and financial services professionals alike are increasingly using social media for a variety of business purposes. Social Media may be a new medium, but FINRA’s rules on communicating with the public are still applicable. The rules protect investors from false, misleading claims, exaggerated statements, and material omissions…
“Firms and their registered representatives must retain records of communications related to their ‘business as such.’ The ‘business as such’ requirement is based on the content of the communication not the type of device or technology used to receive or send the communication. These records must be preserved for a period of not less than three years…
“Firms must have the ability to supervise the business-related content associated persons are communicating on these sites, including possible suitability determinations if recommendations are made. A registered principal must review prior to use any social media site that an associated person intends to use for business. The principal may only approve a social media site if the principal has determined the associated person can and will comply with applicable rules…”