This is going to be a sad one, folks.

Over the past two days of trading, business-to-business (B2B) e-commerce pioneer Commerce One (NASDAQ:CMRC) has lost more than 70% of its already debatable value. The reason: On Thursday, the company filed a Form 8-K with the SEC informing the regulator that it: (a) has just $700,000 left in the bank; (b) remains "significantly" cash flow negative; (c) has failed to find anyone willing to lend it money or buy new shares; (d) anticipates liquidating its business; and (e) expects that after paying off all of its creditors, there will be nothing left to distribute to shareholders.

In other words, "Commerce One is doomed. Abandon all hope, ye who invested there." Given the grave nature of these announcements, the wonder is not that Commerce One's stock price tanked 62% in a single day. Or that it fell another 26% the next day. The wonder is that the stock did not immediately go to zero.

I find that simply amazing. In no uncertain terms, the company told investors that its days were numbered and its stock was worthless. Yet 6 million shares of the stock traded hands on Thursday. Sellers were still able to find buyers for these worthless slips of paper.

The next day, Commerce One continued with the bad news. It laid off 56 of its last 92 employees, paying severance of about $3,600 a head, and announced that after paying a few more bills its cash would be down to $300,000. That's right. In one day, Commerce One burned through more than half of its remaining cash. Investors couldn't say Commerce One didn't warn them.

If you're a Fool and if, for whatever reason, you still own Commerce One stock, I have one word of advice for you: Sell. Yes, I know you lost a lot of money on this stock. But it's not coming back. The company said so itself. If you sell now, perhaps the sales price will be enough to at least pay your broker's commission. Take your losses, and get on with your life.

Don't repeat past mistakes. Learn from them by reading how Commerce One rose and fell:

Fool contributor Rich Smith owns no shares in Commerce One, but he used to own Winstar, which went bankrupt and is now a unit of IDT Corp. (NYSE:IDT), so he knows whereof he speaks.