These Diamond Self-Select lines enable those familiar with 3-1-1, shoes off, and laptop open to breeze into the concourse bypassing the hysterics of cranky people as they perform circus acts.
What I wonder though is who, if the sign is readily placed, would say "I'm not an expert?" Especially if the line is much shorter. Perhaps that's the reason for hiding it. Some suggest airline status (such as an Elite member) should be the criterion for using that line, however those such as myself, who are familiar with the "code" would be forced to endure vomiting babies, and senior citizens crapping their pants, when my absence from that line would be beneficial to all.
I did find this map showing airports that have them.
In addition here are some additional confirmed cities:
Nashville
Raleigh
Boise
For the time being it appears that the Diamond Lines at airports are for those in the know. Perhaps that's the point. Many people who don't know about them may assume it's a "special" line for privileged people, or require an additional fee. In fact when I first heard about it, I confused it with another TSA product which does cost money, but pre-screens you to bypass security all together. However, Diamond Lanes are free, and anyone can use them, you just have to know that they're there.