The cover headline of this week's Barron's reads, "Oil Bubble: When It Will Pop and Why." The article outlines the trends behind oil's run-up, and why these trends could reverse to cause the bubble to pop, bringing prices down to $100 per barrel. Six months ago, oil was trading in the low $90s, and the big debate was whether or not it would break above $100. Today, we're talking about a potential bursting of the bubble, bringing prices back down to a 'more reasonable' level of $100. What a difference six months makes.