My MacBook 15" Retina (Mid 2012) has never had any fan problems. But on 2013-03-30 (I believe) the fans started to give an annoying noise, which only stops when powering down. It is a constant noise that is there regardless of what processes are running on the machine. From SystemInformation/Software/Installations (date sorted), I can see that an SMC update has been installed on 2013-03-24. Data points: I have now installed the app "System Monitor" which reports that both left and right fan run at approximately 2000 RPM (and CPU temperature is 36C). Is that normal? My question is, can the SMC update have caused this problem?