Are RAM coolers really effective?

A fan works for several reasons as I understand it - true for a fan in a room, on RAM, around a heatsink (AC unit, car radiator), for your body, anything.

First it moves the heated air from the area directly next to the source of the heat, making the general area cooler. By moving the hotter air to an area of cooler air, it speeds up the natural process of the Zeroth Law of Thermodynamics by helping the total volume of air reach the same temperature.

By lowering the temperature of the air near the surface of the RAM or its heatsink, it allows the heatsink to dissipate its own heat more easily into that local air. This process is similar to your skin's cooling by sweating. And when you blow a fan on your face when sweating, even though the air around you is equally hot, the process of evaporation works more efficiently and you get cooler. The same process is involved, without the water, for a heat sink with a fan blowing on it.

Even if the source of the air for a RAM fan is hotter than the overall air temp in the case, the processes above will likely overcome it. That is, if you're blowing the hot air rising off the CPU or a hard drive towards the RAM it still gains from the process. This is why a CPU cooler fan that blows the hot air off the RAM across a less-hot area of the motherboard will cool that area off also.

The nature of moving air really doesn't allow the heat to stay close to the chips. The air will find an outlet, cooling the RAM. You can't smother the RAM with its own heat with a fan, the way you might with a blanket.

If you've seen some article that says a fan might do what you said, I'd doubt it and would enjoy reading the article. I'd say it means the author didn't understand much basic science.