Precaution before getting a whiteboard: carpet stains?
If this is for adults only I wouldn't be worried about it.  I have a large dry-erase board in my office that my family uses and light tan carpet and we have never had an issue.  The key is making sure you whiteboard has a tray to put the markers in and not to leave markers open (which dries them out).

If for kids I would say you run the same risk as them coloring with markers at a table.  Certainly they will destroy things and make a mess.  I specifically left certain things off my house to-do list until my kids got older.  

Either way if you want piece of mind I would scotch guard the entire area.  I would use interior automotive spray which I use in all my cars and did my kids carpets with them.  A couple of layers and basically you can spill anything within reason on the floor.