I must confess that when started programming I more or less logged all details as described by "Dillie-O".
Believe me... It helped a lot during initial days of production deployment where we heavily relied on log files to solve hundreds of problems.
Once the system becomes stable, I slowly started removing log entries as their value add started diminishing. (No Log4j at those point in time.)
I think, the ratio of code-to-log entries depends on the project and environment, and it need not be a constant ratio.
Nowadays we've lot of flexibility in logging with packages like Log4j, dynamic enabling of log level, etc.
But if programmers doesn't use it appropriately, such as when to use, when NOT to use INFO, DEBUG, ERROR etc. as well as details in log messages (I've seen log message like, "Hello X, Hello XX, Hello XXX, etc." which only the programmer can understand) the ratio will continue to be high with less ROI.
