1. 10.96 DU
2. 9.77 ericb
3. 9.73 delmoi
4. 8.89 Marisa Stole the Precious Thing
5. 8.65 amberglow
6. 8.45 klangklangston
7. 8.44 Joe Beese
8. 8.18 Blazecock Pileon
9. 8.10 The Whelk
10. 8.06 Artw
11. 7.52 cortex
12. 7.41 flapjax at midnite
13. 7.31 Astro Zombie
14. 7.17 Burhanistan
15. 7.07 languagehat
16. 7.02 jonmc
17. 6.54 five fresh fish
18. 6.27 Ambrosia Voyeur
19. 6.02 Mister_A
20. 6.00 caddis
21. 5.72 Smedleyman
22. 5.68 UbuRoivas
23. 5.61 desjardins
24. 5.56 homunculus
25. 5.45 bugbread
26. 5.41 not_on_display
27. 5.31 Pope Guilty
28. 5.30 Sys Rq
29. 5.20 stavrosthewonderchicken
30. 5.05 Fuzzy Skinner
31. 5.01 Alvy Ampersand
32. 4.92 grouse
33. 4.89 loquacious
34. 4.81 OmieWise
35. 4.68 ThePinkSuperhero
36. 4.66 mathowie
37. 4.55 quonsar
38. 4.52 shmegegge
39. 4.48 Miko
40. 4.47 damn dirty ape
41. 4.46 Ethereal Bligh
42. 4.36 LobsterMitten
43. 4.33 terranova
44. 4.25 bardic
45. 4.23 jessamyn
46. 4.21 amyms
47. 4.20 Abiezer
48. 4.20 Civil_Disobedient
49. 4.17 Brandon Blatcher
50. 4.15 orthogonality
51. 4.06 rtha
52. 4.05 odinsdream
53. 3.99 dhartung
54. 3.97 Pastabagel
55. 3.91 ikkyu2
56. 3.83 pyramid termite
57. 3.82 tkchrist
58. 3.81 PhoBWanKenobi
59. 3.67 Dave Faris
60. 3.66 ROU_Xenophobe
61. 3.62 Kirth Gerson
62. 3.60 It's Raining Florence Henderson
63. 3.59 y2karl
64. 3.50 matteo
65. 3.47 Dizzy
66. 3.46 kindall
67. 3.33 goodnewsfortheinsane
68. 3.32 mediareport
69. 3.31 burnmp3s
70. 3.31 dersins
71. 3.29 quin
72. 3.29 Pollomacho
73. 3.27 mr_crash_davis
74. 3.18 Mitheral
75. 3.17 troutfishing
76. 3.14 Eideteker
77. 3.14 scarabic
78. 3.12 davy
79. 3.04 desuetude
80. 3.00 Chuckles
81. 2.99 ParisParamus
82. 2.96 Faint of Butt
83. 2.93 psmealey
84. 2.92 fenriq
85. 2.92 fandango_matt
86. 2.91 Afroblanco
87. 2.88 salvia
88. 2.88 dobbs
89. 2.87 konolia
90. 2.85 CitrusFreak12
91. 2.84 maxwelton
92. 2.82 dios
93. 2.82 The Deej
94. 2.80 The World Famous
95. 2.75 Balisong
96. 2.69 loiseau
97. 2.68 paulsc
98. 2.68 Plutor
99. 2.64 Mr. President Dr. Steve Elvis America
100. 2.37 XQUZYPHYR

1. 1156 mathowie
2. 1075 homunculus
3. 602 jonson
4. 561 Postroad
5. 500 jaden
6. 495 y2karl
7. 460 MiguelCardoso
8. 417 madamjujujive
9. 394 crunchland
10. 381 Steven Den Beste
11. 346 owillis
12. 334 flapjax at midnite
13. 321 amberglow
14. 320 plep
15. 306 skallas
16. 305 kirkaracha
17. 300 hama7
18. 290 wendell
19. 286 srboisvert
20. 284 XQUZYPHYR
21. 264 matteo
22. 261 semmi
23. 257 Kattullus
24. 254 feelinglistless
25. 227 mr_crash_davis
26. 223 Joe Beese
27. 220 baylink
28. 206 caddis
29. 203 tellurian
30. 202 anastasiav
31. 201 troutfishing
32. 200 mediareport
33. 198 blahblahblah
34. 194 Pretty_Generic
35. 191 amyms
36. 188 Gyan
37. 187 goodnewsfortheinsane
38. 176 delmoi
39. 176 loquacious
40. 176 riffola
41. 173 nthdegx
42. 171 dobbs
43. 170 fenriq
44. 169 specialk420
45. 165 tranquileye
46. 163 ericb
47. 159 brownpau
48. 159 plinth
49. 159 moonbird
50. 158 psmealey
51. 150 Wolfdog
52. 149 insomnia_lj
53. 148 monju_bosatsu
54. 143 orthogonality
55. 142 Artw
56. 139 Blazecock Pileon
57. 138 kliuless
58. 137 WolfDaddy
59. 136 ZachsMind
60. 131 spock
61. 128 dhruva
62. 126 Effigy2000
63. 124 Voyageman
64. 123 grabbingsand
65. 123 adrober
66. 119 lagado
67. 118 tiaka
68. 117 OmieWise
69. 117 fandango_matt
70. 116 rschram
71. 115 ColdChef
72. 113 signal
73. 112 carter
74. 112 KevinSkomsvold
75. 111 holgate
76. 110 aaron
77. 110 Mwongozi
78. 109 tamim
79. 109 Brilliantcrank
80. 108 taz
81. 108 Ufez Jones
82. 106 klangklangston
83. 105 quonsar
84. 105 grumblebee
85. 104 jonp72
86. 103 dersins
87. 103 nofundy
88. 103 hadjiboy
89. 101 gman
90. 100 jonmc
91. 100 tdecius
92. 100 me3dia
93. 100 Irontom
94. 98 peacay
95. 97 magullo
96. 96 not_on_display
97. 95 Astro Zombie
98. 94 Miko
99. 93 languagehat
100. 92 Brandon Blatcher

1. 24608 delmoi
2. 19236 amberglow
3. 16212 jonmc
4. 15936 homunculus
5. 12202 ericb
6. 11643 five fresh fish
7. 10250 dhartung
8. 9778 languagehat
9. 9014 Artw
10. 8981 quonsar
11. 8660 Smedleyman
12. 8353 flapjax at midnite
13. 7768 y2karl
14. 7485 matteo
15. 7462 DU
16. 7194 ZachsMind
17. 7041 caddis
18. 6964 ParisParamus
19. 6838 stavrosthewonderchicken
20. 6661 mr_crash_davis
21. 6566 pyramid termite
22. 6385 troutfishing
23. 6056 Astro Zombie
24. 5959 cortex
25. 5953 kirkaracha
26. 5851 psmealey
27. 5800 jaden
28. 5792 Blazecock Pileon
29. 5772 Postroad
30. 5710 clevershark
31. 5705 klangklangston
32. 5702 quin
33. 5672 UbuRoivas
34. 5610 fenriq
35. 5608 Civil_Disobedient
36. 5564 XQUZYPHYR
37. 5537 bardic
38. 5463 rushmc
39. 5376 tkchrist
40. 5143 mathowie
41. 5118 kindall
42. 5112 Pollomacho
43. 5084 wendell
44. 5065 skallas
45. 5051 loquacious
46. 5040 bugbread
47. 4970 ROU_Xenophobe
48. 4720 mediareport
49. 4658 ColdChef
50. 4509 srboisvert
51. 4239 soyjoy
52. 4216 pracowity
53. 4203 Joe Beese
54. 4189 KirkJobSluder
55. 4173 lodurr
56. 4089 sonofsamiam
57. 4075 nofundy
58. 3858 mr_roboto
59. 3760 shmegegge
60. 3701 mrgrimm
61. 3649 jpoulos
62. 3638 thomcatspike
63. 3622 OmieWise
64. 3521 MiguelCardoso
65. 3510 raysmj
66. 3478 Ethereal Bligh
67. 3458 madamjujujive
68. 3458 Mister_A
69. 3456 Balisong
70. 3423 owillis
71. 3384 Faint of Butt
72. 3345 Pope Guilty
73. 3324 holgate
74. 3256 Pastabagel
75. 3229 orthogonality
76. 3220 davy
77. 3167 Mitheral
78. 3138 George_Spiggott
79. 3129 jfuller
80. 3115 Burhanistan
81. 3109 jonson
82. 3076 Mayor Curley
83. 3046 dobbs
84. 3021 Miko
85. 3014 Space Coyote
86. 2955 dejah420
87. 2934 odinsdream
88. 2928 crunchland
89. 2910 dios
90. 2877 konolia
91. 2867 Heywood Mogroot
92. 2865 Alvy Ampersand
93. 2836 yhbc
94. 2813 alumshubby
95. 2789 brundlefly
96. 2773 Pretty_Generic
97. 2758 davidmsc
98. 2719 dreamsign
99. 2701 rcade
100. 2625 fandango_matt

Excellent question. It is simply the sum of all the times a user has posted on Metafilter (comments or threads on the blue, gray and green) divided by the number of days they have been a member.

Tamim's user profile discusses the idea and while reading this discussion I saw moz's reference to tamim's user page. After reading that and seeing tamim's suggestion, I wrote a quick script to do it. If you see any problems please let me know.