I think one of the reason we have so many unanswered questions is because vagrant users come by --> ask a question --> get answer and never bother to come back and understand/ know how to vote ( or care).
You know something like " Hey someone took the time to answer your question on WPSE, it would be great if you took the time to respond or give them credit."
Just an idea, I know email can be a touchy subject, but we also have a drive-by question problem.
Edit** Here are some WPSE stats.
Category Users Total Rep Avg Rep % Users % Rep
--------------- ------- ---------- ---------- ------- ------
All 7,356 604,710 82.21 100.0% 100.0%
Rep>1 4,553 601,907 132.20 61.9% 99.5%
Rep>10 3,807 597,651 156.99 51.8% 98.8%
Rep>100 2,706 564,470 208.607 36.8% 93.3%
Rep>1,000 50 214,671 4,293.42 0.7% 35.5%
Rep>10,000 4 75,241 18,810.25 0.1% 12.4%
Rep>100,000 null
Rep<10 3,518 6,749 1.92 47.8% 1.1%
Rep<100 4,648 40,040 8.61 63.2% 6.6%
Rep<1,000 7,306 390,039 53.39 99.3% 64.5%
Rep<10,000 7,352 529,469 72.02 99.9% 87.6%
[10..100] 1,132 33,491 29.59 15.4% 5.5%
[100..1,000] 2,658 349,999 131.68 36.1% 57.9%
[1,000..10,000] 46 139,430 3,031.09 0.6% 23.1%%
Raw query aren't saved so it's from:
Here
Using this query
4,553 users with 1 rep or under (61.9%), also there is a cliff between rep 100 --> rep 1000