Out of curiosity, I wrote a little script that counted how many people have spec'ed each skill as a primary, secondary or tradeskill. Only characters who have at least one stat maxed out were counted (the reasoning being that new characters probably wouldn't know what skills they want yet.) Interpret this information however you want to...
Total characters: 1324
Total characters counted in this study: 878
<table border=1><tr><td>Skill</td><td>Primary</td><td>Secondary</td><td>Tradeskill</td></tr><tr><td>Alchemy</td><td>92</td><td>14</td><td>0</td></tr><tr><td>Anatomy</td><td>44</td><td>161</td><td>0</td></tr><tr><td>Animal Lore</td><td>83</td><td>35</td><td>0</td></tr><tr><td>Parry</td><td>148</td><td>234</td><td>0</td></tr><tr><td>Blacksmithy</td><td>45</td><td>4</td><td>109</td></tr><tr><td>Peacemake</td><td>5</td><td>5</td><td>0</td></tr><tr><td>Camping</td><td>5</td><td>51</td><td>0</td></tr><tr><td>Woodworking</td><td>14</td><td>18</td><td>56</td></tr><tr><td>Cartography</td><td>3</td><td>12</td><td>56</td></tr><tr><td>Cooking</td><td>16</td><td>7</td><td>64</td></tr><tr><td>Detect Hidden</td><td>2</td><td>15</td><td>0</td></tr><tr><td>Leadership</td><td>135</td><td>32</td><td>0</td></tr><tr><td>Invocation</td><td>151</td><td>157</td><td>0</td></tr><tr><td>Healing</td><td>33</td><td>337</td><td>0</td></tr><tr><td>Fishing</td><td>4</td><td>6</td><td>118</td></tr><tr><td>Hiding</td><td>16</td><td>30</td><td>0</td></tr><tr><td>Provocation</td><td>46</td><td>13</td><td>0</td></tr><tr><td>Inscription</td><td>23</td><td>11</td><td>125</td></tr><tr><td>Lockpicking</td><td>92</td><td>44</td><td>0</td></tr><tr><td>Magery</td><td>379</td><td>200</td><td>0</td></tr><tr><td>Magic Resist</td><td>104</td><td>513</td><td>0</td></tr>
<tr><td>Tactics</td><td>337</td><td>146</td><td>0</td></tr><tr><td>Musicianship</td><td>22</td><td>27</td><td>0</td></tr><tr><td>Poisoning</td><td>38</td><td>8</td><td>0</td></tr><tr><td>Archery</td><td>50</td><td>33</td><td>0</td></tr><tr><td>Necromancy</td><td>36</td><td>44</td><td>1</td></tr><tr><td>Stealing</td><td>6</td><td>2</td><td>0</td></tr><tr><td>Tailoring</td><td>13</td><td>8</td><td>103</td></tr><tr><td>Taming</td><td>111</td><td>22</td><td>0</td></tr><tr><td>Tinkering</td><td>30</td><td>8</td><td>112</td></tr><tr><td>Tracking</td><td>0</td><td>8</td><td>0</td></tr><tr><td>Swordsmanship</td><td>239</td><td>54</td><td>0</td></tr><tr><td>Macefighting</td><td>73</td><td>73</td><td>0</td></tr><tr><td>Fencing</td><td>85</td><td>32</td><td>0</td></tr><tr><td>Wrestling</td><td>2</td><td>3</td><td>0</td></tr><tr><td>Lumberjacking</td><td>29</td><td>20</td><td>46</td></tr><tr><td>Mining</td><td>47</td><td>11</td><td>86</td></tr><tr><td>Meditation</td><td>50</td><td>223</td><td>0</td></tr><tr><td>Stealth</td><td>29</td><td>14</td><td>0</td></tr></table>
P.S. I'm going to look into that person who somehow has necromancy as a tradeskill...
*edited to make it a bit easier to read