How does Web of Trust measure aptitude and merit? Those two links just go to Wiktionary and Wikipedia. They are therefore an inaccurate definition of WOT's measurement.
Answer: The more consistent your ratings are with the ratings of the site, the greater your rating "merit". For example, if on google.com's scorecard you rated it red in all the categories, the ratings are so far from the current ratings they would hold little or no weight on the site's overall reputation. If you rate consistently with the sites reputation all the time, then your merit will increase and your ratings will gradually hold more weight. However this takes a long time and many ratings.