The subset that you can get birth years off the first page of a google search of their name (n=9), has a pretty clear correlation with younger people believing in harder takeoff. (I'll update if I get time to dig out other's birth years.)
Cool. Another interesting question would be how the views of a single person change over time. This would help tease out whether it's a generational trend or a generic trend with getting older.
In my own case, I only switched to finding a soft takeoff pretty likely within the last year. The change happened as I read more sources outside LessWrong that made some compelling points. (Note that I still agree that work on AI risks may have somewhat more impact in hard-takeoff scenarios, so that hard takeoffs deserve more than their probability's fraction of attention.)
http://reducing-suffering.org/predictions-agi-takeoff-speed-vs-years-worked-commercial-software/