What: Units of LINN Energy (LINEQ) slumped more than 20% by 3:00 p.m. EST on Thursday. Fueling today's sell-off was another analyst downgrade implying that the company no longer has any value.

So what: LINN Energy has been on an unbelievably wild ride this month. Units slumped nearly 70% after the company threw in the towel by announcing that it was seeking strategic alternatives for its capital structure, and maxing out its credit facility. The stock, however, has recovered by almost 50% since that time, before today's downgrade knocked the wind out of its sails.

Today's downgrade is from Wells Fargo, which is cutting the company from market perform to underperform. That downgrade follows closely behind a similar one on Friday by Citi, which cut LINN Energy from neutral to sell. In both cases, LINN's price target was slashed all the way to zero, effectively saying that bankruptcy is in its future.

In fact, both see a growing possibility that not only LINN Energy, but other upstream MLPs, could default on their debt within the next 12 to 24 months. Because of this, LINN and its peers have zero future equity value according to analysts, especially once its oil and gas hedges run out during the next year or two.

Now what: It's really not looking good for LINN Energy right now. The company has a mountain of debt to address, and precious little liquidity to see it though until oil prices rebound. Unless oil prices mount a fierce rally in the very near future, LINN Energy's chances of making it through this downturn are growing dimmer by the day.