I have run into more than one situation in maintaining code (one other developer, specifically) that started throwing a lot of warnings when he turned on warnings where the warning was quite useful. This person found that the best way to get rid of these "useless" "unitialized" warnings was to pipe his error logs through grep -v uninitialized. (He was not at the company six months later.) When I went into the code, I found that he was testing against a typoed hash key. This was a subtle bug that was not discovered for *YEARS* until warnings were turned on.
Sr. Software Engineer, DAS Lead