Adjacent equalizer bands interact, making careless boosting degrade the result.

Evidence

Equalizers therefore have a broad application in the processing of sound. However, despite their utility, they must be used with caution—first to avoid extremes of sound character, unless that is desired, and second to avoid unwanted interactions between different equalizer frequency ranges. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2440