I've just been playing with some cheap 120V E27 9W LED lamps. A Philips for $2.50 easily runs at low power with a .05uF capacitor in series or a 70,000 ohm resistor. That is like a neon lamp! I have one in the basement operating at milliwatt power levels so the dog can see the steps at night. Looking with a scope it is a simple full wave bridge with a resistor in series and a smoothing cap. The current spike indicates a capacitor being charged. Turn on is at about 80V so these lamps could be used with a boost converter with that much DC voltage. I tried operating the lamp with a diode in series to create half wave rectification. This is not only a simple method for dimming but indicates a capacitor is not used in place of a dropping resistor. Top trace is current and lower is voltage. This lamp would start to illuminate at 60VDC.
Tried a capacitor in series with a $2 Zilotek in an identical looking package. That unit would repeatedly flash at about a half second rate. That would have been nice for Holoween. Obviously this has an electronic ballast that waits for a capacitor to charge up before the inverter starts. I thought with an inverter circuitthe starting voltage might be a lot lower. However, it would only start once it reached 90VDC and after that itneeded 75V to maintain an on condition.
A capacitor in series with a $3.50 FEIT 7.3W failed to light at all. That unit would not turn on till 115VDC was reached. The transition to on was smoth and likely does not have any active electronics. It likely hasan anti ghosting resistor to prevent the lamp from lighting due to capacitive effects. In another 3.5W spot the anti ghosting resistor consumed about a quarter watt. This lamp obviously has a LED string of over 100V.
I imagine that these LED lamps will suffer some of the same issues as the low cost CFL lamps. Both lamps with plastic bases have a 9-10 year rated life expectancy with three hours use a day. That indicates they know the LED is being over driven at a high temperature. The base of the lamps get quite hot and only has plastic to transfer heat. The FEIT has a finned metal base and at least makes an effort to remove heat from the LED. I don't remember the declared operating life on the packaging, but it seemed a lot longer like double that of the other two lamps. In just this small sample of lamps it was interesting to see totally different design approaches.