The WOT system is meritocratic. We have designed the system to analyze each user's rating behavior from several aspects, including statistical modeling, in order to determine their trustworthiness. When you start using WOT, your ratings have minimal weight, but if you keep rating sites consistently, your ratings grow more trustworthy over time. The idea is to make the system difficult to manipulate.
It is important to notice that a user's trustworthiness doesn't depend on the number of ratings or whether you agree with other users. Specifically, it's not related to your activity score or user level, which simply tell you how active you've been. There are cases where a user has been active but is not considered trustworthy by the system and thus the user has less rating weight. Also note that all user ratings do have a weight and a single user (no matter how trustworthy) has a limited effect on WOT reputation ratings.