Mi Yodeya: students (posted a Q that got upvoted) 441, supporters (upvoted something) 456, teachers (posted an A that got upvoted) 453.
That's a ratio of about 1 : 1 : 1.
Scifi: 1375, 2767, 1934; .5 : 1 : .7
Rpg: 733, 1530, 1034; .5 : 1 : .7
Ux: 2262, 5059, 2319; .4 : 1 : .5
Diy: 2140, 2167, 1064; 1 : 1 : .5
Bicycles: 846, 1392, 902; .6 : 1 : .6
This seems to imply we have (compared to those sites (except diy)) few lurkers.