Once again, as Wall Street waits for happy hour, we Fools wade into 8-K filings that, if the timing is to be believed, executives would rather you not read.

Kicking off today's list is this filing from Horizon Offshore (NASDAQ:HOFF), which said it's being sued over its prospective sale to Cal-Dive International (NYSE:DVR) for $650 million. Shareholders apparently want more.

Meanwhile, Synopsys (NASDAQ:SNPS) investors should be celebrating. As this filing describes, the Securities and Exchange Commission no longer has questions for the firm, which it had been investigating for goof-ups in its financial statements. Sweet. Break out the bubbly.

The pinnacle of lunacy
The same can't be said for investors in Pinnacle Airlines (NASDAQ:PNCL), which, according to this filing, may spend up to $30 million repurchasing stock under a 10b5-1 trading plan.

For selling, these plans can be great, because they prevent executives from making decisions based on insider information. For buying, well, not so much.

Think about it. By abdicating trading authority, Pinnacle executives are acting as if their company's stock is a birthday pinata. Just put on the blindfold and swing wildly till the candy starts flying!

But here's the thing: What if the pinata is empty? Or, worse, a live donkey?

Buybacks only create value when the stock being targeted is repurchased at a discount. Too often that's not the case, as my Foolish colleague Rich Smith points out in skewering billion-dollar buybacks at Staples (NASDAQ:SPLS), Target (NYSE:TGT), and Symantec. (Read all about them here, here, and here.)

Pinnacle, which trades for less than eight times its forward earnings, may be cheap. Then again, free cash flow has declined dramatically every year since 2003.

So, is Pinnacle a bargain? Insiders don't seem to think so. They've sold more than $3 million worth of stock since June 1, with all but $318,143 of that derived from vested stock options grants, according to Form 4 Oracle. 

Translation: Who cares if the stock is cheap? We just want to be able to exercise options without appearing to dilute existing owners.

Buying back a bonus
But my favorite filing this week comes courtesy of the board of directors of disk drive maker Western Digital (NYSE:WDC), which announced changes to its executive bonus plan in this filing. Quoting:

For the six-month period beginning June 30, 2007 and ending December 28, 2007, the Compensation Committee selected earnings per share as the financial performance goal ... At the end of the 6-month performance period, the [bonus plan] will fund in an amount ranging from 0% to 200% ... [Emphasis mine.]

Let's address the good news first. Before the change, executives were promised between 75% and 100% of their base salary. Now, with 0% as a possibility -- how real a possibility is anyone's guess -- there's an extra incentive for managers to perform.

But I wouldn't rush to buy this stock. Quoting from Western Digital's recent quarterly financial filing:

Our Board of Directors has authorized us to repurchase $250 million of our common stock in open market transactions ... Since the inception of our stock repurchase program through May 4, 2007, we have repurchased 11.7 million shares for a total cost of $143 million (including commissions). We may continue to repurchase our stock as we deem appropriate and market conditions allow. [Emphasis mine.]

Translation: We may boost EPS any time by repurchasing shares with your money.

With 200% bonuses on the line, my guess is that Western Digital will be buying back shares for many years to come.

Think you've found a late filing we Fools should see? Let me know.

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Fool contributor Tim Beyers, who is ranked 5,179 out of more than 30,800 rated investors in our Motley Fool CAPS investor intelligence database, usually favors two scoops of ice cream over the inside scoop. Tim didn't own shares in any of the companies mentioned in this article at the time of publication. Tim's holdings can be found at his Fool profile. His thoughts on SEC filings, Foolishness, and investing in general may be found in his blog. The Fool's disclosure policy may be filed under "F" for fair, or Foolish.