Seriously, though, it is amazing how easy it is to socially engineer your way past any security.
My job involves going to a supermarket checkout and asking "hi, where's the staff entrance?", and being directed to it, then saying "hi, I'm here to replace your routers" whereupon I sign the visitors book and am left to my own devices with racks 'n' racks of server and networking equipment. Often after the staff say "oh, we had no idea you were coming". Today I even left my tool trolley next to the racks and asked "is there a loo I can use?" and was directed where to go.