I think 9 times out of 10 I would fail a whiteboard coding exercise based solely on my bad handwriting... which is even worse when done with a fat marker on a vertical surface. In my day-to-day work I am rarely (if ever) required to actually write something down that others will need to read... so my bad penmanship is a non-issue. If you want me to whiteboard something in an interview perhaps provide a computer projected onto the whiteboard (or what ever tech you have) so everyone can see and let me type my response while we talk?

I have a keyboard... and I know how to use it.