Our boy is back.

My inbox is filled with MannKind (MNKD_) supporters heckling me for being wrong about the stock. Tim H. is representative:

You have recently written about the predicted failure of MannKind and its shares. You even used some diabetes "expert" to further your views. But, it seems you failed. The shares have exploded in the last 2 1/2 months. I suspect you have lost a lot of relevance (assuming you had some at some point). $1.75 Billion now.

Mannkind's stock price is up $190% this year so I can understand why Tim H. wants to declare victory over the bears. But stocks are fickle, they go up and down. Mannkind shares did a lot of the latter this week, falling 15% through Thursday.

The run-up in Mannkind's stock price ahead of this summer's Afrezza clinical trial results does not prove bulls or bears right. Let's wait to see how the story plays out.

My friend and CNBC commentator Herb Greenberg said it best this week -- Don't Get Fooled by a Stock's Price:

In my decades of reporting on stocks and the markets, among the many things I have learned: Just because a heavily shorted stock is up--or a heavily promoted stock is down--doesn't necessarily prove the original investment thesis or concern is wrong.

There are always exceptions, of course, and this dynamic is often magnified for those of us who sit next to a computer all day watching our stock screens, headlines and social news feeds.

Still, the mechanics of the markets have changed. With unprecedented volatility and the speedy exchange of information on the likes of Twitter, for many investors chest-thumping and hubris, as well as anguish and despair, over every favorable or unfavorable tick trumps green eyeshades and patience. Emotion gets amplified, not reason.

In the process, the definition of success, failure, victory and defeat is now often compressed into days if not hours, and anybody who doesn't buy into the concept is considered a loser or, worse, a fool.

Trading around the charts and pinpointing the exact point of entry and the fastest exit has become standard operating procedure, with old-fashioned buy-and-hold "investing" relegated to laughing stock status. The concept of long-term short-selling appears to have all but disappeared. Most who practiced it exclusively as a profession either have quit or have been carried out on stretchers.

Yet underlying stock stories, notably short or value-oriented longs, can take more than a few weeks or months to bear out. Some take years.

Wise words. The Mannkind story is far from decided.

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