No, not problems with employees and social media - this problem is of the firms' own making. Many web sites allow users to log in to the site using their Twitter, Facebook or LinkedIn account. It makes the log in process easier for the user, they don't have to remember additional passwords, and simply click a link to use their social media account to log in.
Apparently the banks and brokerage firms are considering using social media logins for their customers - giving their customers faster and easier access to their account information. The problem? The hacking of Twitter, Facebook, LinkedIn or other social media sites. A hacker gets into a social media account, and if the user's brokerage firm allows a social media login, the hacker has access to the customer's account.
Definitely not a good idea.