I switched to paleo 7 days ago, I've been slightly constipated (no discomfort but only going once every two days.
Tonight I cheated and had too much dark chocolate and felt sick in the stomach straight away. Around 2 hours latter I had to rush to the bathroom. I was under the belief that it takes approx 14 hours for food to pass through but it just seems to much of a coincidence
I find dark chocolate goes through me quickly, too. Most foods take 6 or more hours to give me a gluten reaction (diarrhea), but dark chocolate with trace amounts of gluten takes about 20 minutes to give me a gluten reaction. I suspect it's because I typically eat chocolate by itself, and it melts into a liquid fairly quickly in our digestive tract, so I bet it goes through the stomach pretty quickly. Chocolate also contains a number of stimulants, and they probably also contribute to speeding up gut motility (I would guess, at a local level, even).
(Note: I react to very small amounts of gluten, so most chocolate causes me problems. I have no problems with chocolate that has been tested and certified as containing under 3ppm gluten.)