DC offset might be a bad thing sometimes. When wiring an Operational Amplifier, a DC voltage will appear at its output even no voltage difference is applied at its input.
DC offset occurs when hardware,for example, such as a sound card, adds DC current to a recorded audio signal. This current results in a recorded waveform that is not centred around the baseline .
In some cases, when DC-Offset is present, glitches and other unexpected results can occur when sound effects are applied to the audio file. You can compensate for this DC offset by adding a constant value to the samples in the sound file.