AFAIK, all the investment banks (in the US atleast) have a mandatory annual two-week vacation policy for all front-office (traders/sales etc.) employees. Furthermore, you are supposed to be totally switched off during those two weeks (no working via email etc.), the idea being that your colleagues get to see all your work to reduce the chances of you hiding something like the rogue trader at SocGen or Barings.
This is true at all major commercial banks as well, for important enough employees. The vacation is required to pass over the end of the fiscal month, just to be sure.
