I just asked my Facebook how far they think they could walk in 24 hours. Will report back findings.
PREDICTION: Whatever the first response is, later responses will gravitate toward it.
I remember reading about a study where people were asked "What is the population of Poland?" Then they had a plant make the first guess. If the plant said "3,000,000" then the guesses of the non-plants averaged like 7,000,000, and if the plant guessed "80,000,000" then the guesses of the non-plants averaged like 70,000,000.
I think I read this in "Innumeracy" or "A Mathematician Reads the Newspaper" but I could be wrong. Both are great books though imo.
That's called "anchoring", it works with pricing as well.