Each problem in Math and Verbal parts of the forum has a button: Rate it!. If a person clicks on the button, he or she can rate this problem in the scale of score (800,700,600...level), of type (SC,RC,CR,PS,DS), of subtype (Number prop, inequalities....)
In the future, people could make search and chose, for example, only geometry problems of 700-level. I guess it could be improve quality of our learning.
NEW! GMAT ToolKit 2 (iOS) / GMAT ToolKit (Android) - The must have GMAT prep app | PrepGame