This is something that bugs me about whiteboard-style interviews - they test almost none of the typical day-to-day aspects of programming. Without Google, without docs, without a REPL, without the code-run-debug cycle, how is it that you think you're assessing how effective I am in real life?
EDIT: not to mention that you're also not testing me for one of the most important abilities of a coder in a software shop: how well I learn new things.
EDIT: not to mention that you're also not testing me for one of the most important abilities of a coder in a software shop: how well I learn new things.