Ironically, this can actually depress resale prices. When people go to list, they look at existing listings. If there are dozens of "below market" listings playing this game, that can eventually shift the actual market price. Then to get the same "bidding war" effect, sellers have to go even lower. The "incite a bidding war" strategy really only works if there are just a couple listings trying to do it. If there's more than about three, then there's a real chance they're just temporarily driving the market price down.
Most pricing reports that are published by brokers (and DVCforless and DVCFieldGuide) are based on listed prices, not final contract prices. So throwing out a bunch of under-market listings would depress the reported pricing, causing both buyers and sellers to lower their price expectations. That may not always translate to lower contract prices, but it definitely applies downward pressure.