Why is it important to remove surfactants during sample preparation?

Surfactants are difficult to remove from HPLC columns and systems.  They can cause significant changes to the selectivity of your HPLC column by binding to the column surface chemistry irreversibly, and changing the nature of the column.  This leads to high back pressure, poor peak shapes, baseline/retention drift, degradation, lack of reproducibility, etc.  Surfactants can also contaminate your mass spectrometer, leading to signal suppression/enhancement.