[jacquesm]

The pumpers and the dumpers are the same people, pump and dump relates to the two different phases of the fraud, the first where the stock is hyped either by cold calling, spam or some other way to artificially increase demand for an otherwise remarkable stock that was obtained at a very low price. Once the price has gone up enough for the fraudsters to unload they start selling their stock (the dump phase) leaving the investors with a stock worth pennies.

It only works because of the hype ('pump'), and it's pretty rare for a pump to go viral enough that the pumping would be sustained without the perps marketing their trash. That would move their clients into the realm of the pumpers as well.

Think of pump-and-dump as a mini bubble inflated by high pressure marketing to gullible targets.