Is there a technical reason why I cannot find a mini display port to hdmi (female) cable that's more than 6 inches?
I've looked and looked and don't see one. Do they just not exist?
May I suggest that you not look for a cable with a "female" HDMI end on it (those would typically be called "adapters" and would be very short. Instead, look for a full-length cable with mini-DisplayPort to HDMI. Such as:
http://www.monoprice.com/Category?c_id=102&cp_id=10246&cs_id=1024603