I ran across an instrumentation amplifier datasheet from "THAT Corporation", and noticed the polarized capacitor in series with the gain resistor:
It is a typical 3 op-amp in-amp, so the differential input will be seen across the gain resistor, and C1 is meant to avoid changes in dc output offset with gain.
Now, the input is typically a microphone, and the AC voltage can reach 100mV or even a bit more.
For a 2k gain resistor and 6.8uF cap, 10 Hz will be seen with -3dB across the cap: 70 mVAC.
So the question is, will an electrolytic survive and work properly during these small negative excursions?