Sometimes your review for some number should not be visible to other users. There should be more reasons why, here is the explanation of the process we use to publish your reviews.
The Should I Answer application is based on user ratings for unknown numbers. We strongly believe that the only working protection is when people help each other and share the information and experience. Don't keep the experience with unknown numbers for yourself, share it with other users - even in the case someone else already rated the number. More reviews means more help :-)