This is not only true for grad school, but when you look for work too. Before you use somwone as a reference ask them if it's ok. If they don't look like they are happy, you don't have to withdraw your request, just don't list them.
School is an excellent time to learn the value of a good reference!
Job Search Editor, Career Training Editor, Launch ManagerCareer Training SiteJob Search Site
Authentic leaders don't pretend to be anyone other than who they are...