I am doubting that the original Post-it brand is really behind this, but a Japanese company called Actbrise [JP] (slogan: “Seven falls and eight rises.”) is selling a USB stick with a built-in sticky note pad [JP].
The USB 2.0 stick can hold 100 mini notes (50×15mm) and offers 2GB of memory.
It can be pre-ordered for $30 but is Japan-only. I suggest you ask Rinkya, Gizmine or The Japan Trend Shop if you live outside Nippon and really want to get the stick. They might list it if interest is high enough.