Dependencies matter. Every dependency you add to your project is an invitation to break your project.
You send that invitation to the direct dependency author, and every downstream author.
Though the title is dramatic, Code dependencies are the devil provides a great overview of why dependencies should be added with care. It contains a set of questions to help you evaluate whether to add a project as a dependency.
Dirk Eddelbuettel wrote about dependency woes he experienced. He also includes examples of others' experiences.