It's interesting to see the spread between the younger and older folks.
The reddit FI subforum (whose members are mostly <35 years old based on a recent poll) has a similar thread running and the numbers tend towards the lower end (averaging around $1MM, with some ridiculously low ones like $150k and $250k).
The numbers here, where the folks appear to be mostly in their 50s and 60s (based on the stats thread), tend towards $2MM.
I think when you're young and penniless, $1MM is a lot and seems so far out of reach. Once you're grayer and have a couple of pennies to rub together, maybe that $2MM or $5MM isn't too far off and OMY sets in...