[old_tv_nut]

A common deliberate use for the variable emitter impedance is in an IF stage with Automatic Gain Control (AGC). Even then, an emitter resistor is generally used, but the emitter also has an AC bypass capacitor directly to ground. The AGC feedback voltage is applied to the base of the transistor to vary the current in the transistor. This works fine as long as the IF signal is small compared to the DC bias, so the signal itself doesn't cause a variation in gain (which results in distortion). So, you may see AGC applied to the early IF stages and not to the last stage.

Because the video you want to amplify (1 volt) is large compared to the base-emitter drop (0.7 volts) it definitely could cause distortion; but when applied to the combination of the base-emitter junction and the emitter resistor, the emitter resistor keeps things linear.