The now-bankrupt GM's stock price is up almost 100% this week from speculators and short-sellers, forcing the automaker to make a statement reminding people it's, essentially, a worthless piece of paper and shouldn't be bought. Sad, sad press release below.

GM Statement re: recent changes in GM stock price and volume

GM management has noticed a recent elevation in the volume and price of its common stock. While GM does not control the market or its stock price, GM management strongly believes that any recovery for the common stockholders in the chapter 11 bankruptcy process is highly unlikely, even under the most optimistic of scenarios. Stockholders of a company in chapter 11 generally receive value only if all claims of the secured and unsecured creditors are fully satisfied.