Extracted from http://www.monstercable.com/hdmi/the_facts_on_hdmi.asp

HDMI™ Over Long Lengths

Consumers want to save space and hang their new high definition flatscreen TV on the wall. They also want to hide their gear for a clean, sophisticated look.". Of course, that means running longer HDMI™ cables in wall.

It’s now not uncommon to find video components located 25, 50, and even 75 feet away from a TV. This means that data-intensive high definition video and audio must be transmitted over very long distances.

Unfortunately, HDMI™ cables were never designed for this purpose, and performance over long lengths is not specified in the HDMI™ standard. Therefore, highly advanced cable designs are required to meet the performance specifications of HDMI 1.3a, Category 2 and beyond over long lengths