This column was originally published on RealMoney on Sept. 7 at 2:44 p.m. EDT. It's being republished as a bonus for TheStreet.com readers.

Insider buying and selling never tell the full story. Most of the time, I avoid doing anything off either, unless the buying is concentrated and heavy or the selling is poignant after a big move.

Today, though, I am itching to take action in one stock because of insider buying,

Lions Gate

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(LGF)

. And insider selling made me kick out

Pentair

(PNR) - Get Report

, a company that I had owned for my charitable trust,

ActionAlertsPLUS.

Let me explain.

Lions Gate impresses me as one of those companies that wants to make movies to make money, not for ego or to satisfy some innate intellectual quest. Lions Gate recognizes that movies are a form of commerce; you make them for X amount of dollars and want them to generate four or five X.

That's smart. It's also unlike what I see at the other movie houses, where I believe they often have different motivations. So when I saw clustered buying, it caught my attention.

"But, ahh," you say, "

Overstock

(OSTK) - Get Report

has clustered buying, why not like that?" Because I don't care for the business model, and because life is way too short to be caught up in that battleground.

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For Pentair, I wanted to wait to see if it could get some big pump orders out of New Orleans. The last quarter was just OK and the guidance was simply not OK, but Pentair is in the water pump business, so, I figured, why not let it be taken up by the Katrina traders?

The CEO, Randall Hogan, though, couldn't wait. It was revealed Tuesday that

he

filed to sell 30,000 shares last week. You have to figure that if there were some huge orders coming, this guy would know and he wouldn't file to sell. So I stopped hoping and I booted the darned thing.

Now, I know that people sell for a million reasons: divorce, estate planning, prudence. But this stock's well off of its high, and I can't believe that the guy needs the money that badly. Heck, maybe he's donating the proceeds. I don't know, and I don't care. I lost so much faith in the company after that last quarter that the only thing that would have made me keep the stock longer term was a

buy

of 30,000 shares, and I sure didn't see that.

Insider buying and selling are not indicators of anything in the short term. I don't expect Lions Gate to blow away next quarter's box office. I don't expect Pentair to have a big shortfall. But when graphed over the fundamentals for the longer term, I believe insider activity is a valid push if you are teetering in one direction or another.

So, sayonara, Pentair, and, if I could own such small stocks, hello, Lions Gate!

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