Failure to cite landmark studies.
Failure to accurately present the theoretical and empirical contributions by other researchers.
Failure to stay focused on the research question.
Failure to develop a coherent and persuasive argument for the proposed research.
Too much detail on minor issues, but not enough detail on major issues.
Too much rambling -- going "all over the map" without a clear sense of direction. (The best proposals move forward with ease and grace like a seamless river.)
Too many citation lapses and incorrect references.
Too long or too short.
Failing to follow the APA style. American Psychological Association
Slopping writing.