It's a new week, which means it's time to check out the most interesting insider purchases.

After reading through numerous filings using insider tracking tool Form 4 Oracle, here are my top five this week.

The week's buying

Company

Closing Price 10/30/07

Total Value Purchased

52-Week Change

DuPont Fabros Technology (NYSE:DFT)

$21.00

$3,198,300

(7.5%)*

First Horizon (NYSE:FHN)

$25.67

$2,067,251

(34.7%)

International Speedway (NASDAQ:ISCA)

$44.22

$2,946,055

(14.8%)

MGIC Investment (NYSE:MTG)

$19.17

$1,857,706

(67.4%)

Security Bank (NASDAQ:SBKC)

$10.09

$1,532,750

(58.4%)

Sources: Fool.com, Yahoo! Finance, Form 4 Oracle, SEC filings.
*DuPont Fabros began trading on Oct. 19, 2007.

Is there magic in MGIC?
Could MGIC, which less than two weeks ago I dubbed one of the worst stocks in the world, be a (gulp) buy? Not according to our 72,000-strong Motley Fool CAPS community:

Metric

MGIC Investment

CAPS stars (5 max)

*

Total ratings

200

Bullish ratings

70

Bull ratio

35.0%

Bearish ratings

130

Bear ratio

65.0%

Bullish pitches

16

Bearish pitches

7

Data current as of Oct. 31, 2007.

But insiders beg to differ. Seven different executives and board members have purchased shares of MGIC since Friday. CEO Curt Culver led the buying, spending nearly $1 million for 50,000 shares.

What's causing him and his peers to spend so much of their own moola on a stock that, by most accounts, is driving 120 on a highway to oblivion? With the lights off and a thumping dose of AC/DC crashing through the stereo speakers? (As if you don't know what song to which I'm referring. Puh-leeze.)

CAPS investor firemankenny sums it up best, I think: "This stock has taken a beating, and rightfully so, but will recover when the housing market returns to normal. They have large reserves of cash and will tighten the insurance lending standards."

I wish I could be so certain. There's a pretty small variance in the multiples for MGIC and peers like PMI Group (NYSE:PMI). For example, even though MGIC's current stock price values each dollar of revenue at just $0.94, that's only a little less than the industry average of $0.97. PMI, meanwhile, gives shareholders $1.12, but it has long produced better returns on capital.

My advice? Add MGIC to your watch list and wait for signs of a recovery. One may be in the works. But we may also be witnessing the first of several years' worth of losses.

Oh, who needs due diligence?
Even so, I give more credence to the buying at MGIC than I do the insider activity at International Speedway. Even though executives have spent millions to pad their already hefty interests, every one of these purchases was planned. The executives' purchases were made under the auspices of a 10b5-1 trading plan, which keeps insiders from unfairly profiting from insider knowledge in making trades.

I have very few problems with these plans when it comes to selling. After all, executives who hold for years should have no trouble collecting substantial gains without timing the market or any such silliness.

But for buying? Planned purchases suggest an utter lack of due diligence. It's like picking something off the shelf at Tiffany without regard for the price tag. Only the rich, or the terminally stupid, do that.

Besides, it's not as if International Speedway is astoundingly cheap. To the contrary; the stock trades for 32 times its trailing earnings, nearly twice its projected long-term growth rate. Buyer beware.

And that's your update. See you back here next week, when we dig through more insider deals in search of the next home run stock.

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Fool contributor Tim Beyers, ranked 12,402 out of more than 72,000 participants in CAPS, didn't own stock in any of the companies mentioned in this article at the time of publication. Find Tim's portfolio here and his latest blog commentary here. The Motley Fool has a disclosure policy.