The blower and drip pan are visible. This situation was potentially quite serious. The condensate pan was clogged and stagnant condensed water was dripping onto the squirrel cage blower which was aerosolizing the brew. In a similar situation, a friend was nearly poisoned in his car because the defroster blower was spinning in a puddle of engine coolant that was leaking from the heat exchanger at the passenger side. This situation occurs quite commonly when the float valve becomes stuck in an open position due to mineral deposition.
Water overflows the reservoir and rusts some part of the furnace out.
Of the dozens of furnace humidifiers I have observed on inspections, only one was operating. The rest were either stuck in the off position or the drip and destroy position. I even moth-balled my own humidifier, giving up after weekly cleanings and subsequent microscopic investigations that yielded water virtually indistinguishable from pond scum. I have drained humidifiers with such foul odors that they were difficult to remove and dispose of. Most recently, I came upon a neat pile of insulation in a humidifier on a furnace leaking combustion fumes from a rusted out heat exchanger.