Are certain types of home theater conversion/adapter cables really a scam?

[allhailzeppelin]

In the past while looking through HT questions, I've noticed some answers saying that some cables that supposedly allow you to go between formats don't actually work. I can't remember exactly which ones, but I think they were something like HDMI-Component, HDMI-VGA, VGA-DVI, or Coax-RCA audio. I'm guessing it would be due to one being analog and the other being digital. Are there really any cords like these that don't work (or at least not properly)?

 

[GrumpyMac]

The devil is in the details with these cables.

The HDMI to Component cables Do work - but only from a computer to a TV or from a camcorder to a TV where there is no commercial media playing. When you try watching a DVD or streaming of commercial programming - the high-def copy protection kicks in and it wont work.

In the fine print of all these cables is weezle words like "does not support HDCP" or words to this effect - but in such vague terms people buy them hoping they will work.