I've noticed this one for years, and did perform a random sample over the last 4 flights.

Many, many people seem to close their eyes during take-off. Some feign sleep (how can I tell "feigning?" Body language.), others just put their head back and close their eyes. Lots of people put their book down in their lap and close their eyes for take off and then pick their book back up a minute into the flight.

I tested this on my last 4 flights, all in domestic first class looking around during take-off. On two, around half of the people in the cabin closed their eyes. On one, everyone but me had their eyes closed. On one, only 3 of the 8 in the cabin did. Ironically, this was on the red-eye!!!

I suppose that this is more of a way of dealing with stress/fear than a superstition. But now that I've started noticing/looking for this behavior it has proven onmipresent!!!