If it's purely the exchanges themselves, and I'll guess most of the time it is, then that's much more odious.
why is that? with volume pumping, i figure the exchanges are just trying to exaggerate volume and liquidity to attract more traders. some relatively innocuous algorithm that amplifies volumes without necessarily manipulating the market much (since everything is amplified).
if traders are doing it, i assume their intention is always bad. rationally, there's no reason for traders to engage in that behavior unless they are trying to manipulate price.
It is most certainly the traders. Manipulating the price means they profit from the activity. Traders are in it for the profit, not for the altruistic win. It is within the interest of the exchanges to allow Wash Trading, or rather, not disallow or actively monitor for it since this activity is not yet prohibited via regulation. Exchanges are also in it to make a profit. If the traders engage in this behavior then not only do exchanges benefit from the fees derived from the aforementioned, but also the positive side effects from exaggerated volumes.