This post advocates always buying the cheap home theater cables. I agree up to a point. I have never been able to hear the difference in really, really expensive cables, say for 3 foot interconnects.
But there is an exception to this, and it is interesting the author Glen is quoting actually uses this example -- long runs of video cable, particularly HDMI. If your TV sits on top of your video source, and the video run is 6 feet or less, then the average person with the average equipment will not notice the difference in video cables. But should your cable run extend to, say, 25 feet or more, then you are going to have problems. Video is both very high bandwidth and very susceptible to noise. HDMI and other digital cables are no exception -- the only thing that changes are the symptoms.
In an analog cable, you will start getting a lot of video noise with longer cable runs. Computer VGA cables were notorious for this -- if you went more than 6 feet, your picture could be a real mess.
SVGA S-video also had such problems. Now, with digital cable, the picture does not gain noise but at some point the signal is lost altogether and the picture drops out completely -- think of a youtube video streaming over a bad wireless connection. I will about gaurantee this will happen with 25 feet of JC Penny HDMI cable.