As much weight as you decided it deserves.

There is no real way to quantify a degree of trust. A rating is either positive, neutral, or negative. Yes, there is the "risked bitcoin amount", but that is rarely accurate, difficult to verify, and common abused by people wanting to give their ratings more weight. There is no "mild positive" or "strong positive". Trusted and untrusted is simply a function of the design of the trust system, and you might find some untrusted feedback to be more helpful to you than some trusted feedback.

If you are seeing ratings you don't agree with, then it is a good time to think about starting to set up your own custom trust list.