Defending blinds is relatively unimportant in NL cash games, b/c blinds are so small compared to stack sizes. It can be very important in SNGs and MTTs though. In 6-max cash games it's slightly more important, b/c the blinds come around more often. But mainly, defending blinds in cash games is not about the blinds themselves, but about taking advantage of the blind stealers wide range to win their pre-flop raise or their raise plus a c-bet.