Since I always like to be able to take notes on the tablets that I use, I did a quick search and found two apps that can do some very basic inking on the BlackBerry PlayBook: ScratchPad and Sketch Book.
Neither app is ideal for true inking, but for now, it's good enough for basic note-taking, drawing, and general scribbling using a capacitive stylus or your fingertip. See them in action in the video below.
ScratchPad doesn't give you the option to save or email anything you write/create, which makes its usefulness extremely limited and also not worth using at all.
Sketch Book is better because it allows you to save your notes and drawings. It also lets you change the background and ink colors. Unfortunately, like ScratchPad, there's no way to send Sketch Book files by email.
Oh well. At the very least, we can see that some sort of note-taking app is somewhat possible for the BlackBook. The iPad 2 I use has some really good note-taking apps so the limitation here is not the capacitive display. Maybe one day there will be a true inking app in App World.