The plunge in world oil prices in recent weeks has been dizzying. As with all major changes in prices, there are winners and losers in this situation. The biggest potential losers, of course, are the highest-cost oil producers -- Canadian tar sands, "tight oil" and "shale oil," etc. Thus, according to investor website "Seeking Alpha," the ongoing oil price plunge should be making investors in Canadian tar sands "very very nervous." Key points from "Seeking Alpha" include: