TC can only be awarded in three categories for a user, you cant be considered a TC for more than 3 categories. I have no clue how they award TC, except the Yahoo line of being active in a category and giving quality answers. If your in the top 10 answerers you still may not be a TC for that category. I think the only category in racing that has a TC is Nascar, and General.
The flip side of that is there are like a thousand TCs for Polls and Surveys.