Should you ever use protected member variables?

Question

Should you ever use protected member variables? What are the the advantages and what issues can this cause?

Answer 1

The general feeling nowadays is that they cause undue coupling between derived classes and their bases.

They have no particular advantage over protected methods/properties (once upon a time they might have a slight performance advantage), and they were also used more in an era when very deep inheritance was in fashion, which it isn't at the moment.