The one positive I see in publicly showing what you're currently working on is the very starting point of accountability.
Like telling your friends that you're training for a marathon. It adds some pressure to finish things.
Beyond this, personally, I wouldn't see why I would do it.
* I'm talking about adding a /now page. The author Derek Sivers is likely listing people to encourage the movement. I see someone in my field who is doing cool thing, I'd like to do cool things, let's put my money where my mouth is and "get out there."