If you’ve never heard of humans.txt, the official site explains:
It’s an initiative for knowing the people behind a website. It’s a TXT file that contains information about the different people who have contributed to building the website.
Judging by the deleted Wikipedia entry on humans.txt and the rather low numbers on builtwith.org, I’d say it’s not really common enough to have it on your site. On the other hand, some really big sites do use it, some offer you a job through it, some people just use it to joke around.
It seems humans.txt is mostly used as a hidden inside joke, as I don’t think I’ve seen the official logos being used. There is a useful addon for Chrome (and I’m sure other browsers too) that notifies you when a site you are on has a humans.txt.
I personally like it being used for more than just listing your team members. Something along the lines of a bonus content on a DVD or a funny or clever easter egg.
And speaking of easter eggs, I came across this interesting comment by someone describing a “feature” on their site:
I’m a big fan of the Konami code jQuery plugin. On my site, when you put it in you get a better deal on your VPS.
I’m keeping this in mind for the next time I’ll be ordering something online.