For young Wall Street employees who live their lives through social media, working at a big bank can feel as if the plug has been pulled. Most financial firms ban Facebook, Twitter and Gmail, and block most music and video streaming sites. To watch soccer highlights, one analyst said he translated the names of the teams through Google and looked for them on Rutube, YouTube’s Russian equivalent. While firms are able to monitor e-mails and instant messages internally, it is impossible to track what one employee among hundreds of thousands is communicating on Twitter or through a Facebook chat. So …