US Patent Granted On "No Cell Phones" Sign

If I asked an eight year old to draw me a "No Cell Phones" sign, I'm sure he would craft the obvious. However, the US Patent office has just granted a patent for the obvious design. The signs themselves are a good idea for locations where, for whatever reason, mobile phone use should be restricted. Hospitals and dynamite blast zones come to mind. However, do we really need our government to issue a patent on this?