DRM prevents digital data/signals from going where an end-user wants them to. So you cannot play DRMed media on a open-source player, but only players blessed by the DRM-vendor. The end-user has his choices artificially limited.
And now the end-user cannot use any cables he likes. Only those cables blessed by the proprietary connector vendor. You have authentication where none is needed, exclusively to give the vendor power, not to provide the end-user with benefits.
Both are about digital data/signals and having artificial restrictions imposed on them. I think the similarities are good enough to warrant the name DRM.
To the layman it may appear that way, but I assure you the lightpeak cables don't have any DRM logic in them, they merely mux/demux signals. I think you're just a bit misinformed, or think anytime there's chips in basic things like cables, to consider them DRM devices. I suggest you wikipedia DRM to brush up on your definitions.
If there are more adopters of lightpeak, there will be other cable manufacturers, and users can buy any cable they want. People who don't understand electronics also wouldn't understand how this might benefit the user.
Personally, I think lightpeak is a fairly interesting way of implementing something, it enables ports to be a lot more capable without having to replace electronics on the motherboard.
Perhaps users who don't fully understand what is going on inside would prefer to think that it's something evil...
And now the end-user cannot use any cables he likes. Only those cables blessed by the proprietary connector vendor. You have authentication where none is needed, exclusively to give the vendor power, not to provide the end-user with benefits.
Both are about digital data/signals and having artificial restrictions imposed on them. I think the similarities are good enough to warrant the name DRM.