Currently there is no limit to the number of down votes one person can cast.
A similar question was asked at meta and closed there to be asked here. There is a comment saying the question was posted here, but I have looked and can not find it.
This is somewhat based on a related question Is a mass down vote vandalism
If we assume that in a perfect scenario a proposal in search of definition requires 40 questions with 10 up votes each, and each person is limited to 5 votes than it requires 8 people for a single up vote to be scored to each of the 40 question. It requires 80 peoples votes to move a proposal forward. But it only takes 10 people to completely reverse the up votes of those 80 people.
Comments are allowed on questions, so if you truly feel that more than 5 questions are not appropriate there is an avenue to address each question individually.
To me it seems unbalanced to allow a subject's detractor to have 8 (or more) times the voice of a promoter.
Should the down vote limit during 'Definition' phase be the same as the up vote limit?