Elfenbein, who writes about investing at Crossing Wall Street, was named by CNNMoney as "the best buy-and-hold blogger" on the Web. To hear how a long-term-oriented investor has adapted his thinking over time, I expanded the question in the below video exchange. (Run time: 1:39; there's also a transcript below.)
Brian Richards: How has your investment thinking changed over the course of your career -- following stocks, writing about stocks, recommending them?
Eddy Elfenbein: A few things I've learned. One is it's just a truism: The trend can always go further than you expect, further than you thought. "The stock it's down to $9. It can't get any lower." And then it's at $6. And conversely, "it's at $8, it can't go any higher," and then it doubles. And so that's something I've always learned, that that end point is never where you think it's going to be.
And then I think the lesson of humility; I've learned more and more of what I don't know and I've learned to concentrate on the shrinking spheres that I do know, that I feel comfortable. I think when I started out investing I wanted to know everything. I wanted to know how all these companies work, and you know people will ask me about Groupon or this company. I just haven't the faintest idea what they do or how to value them, and I'm fine with that. [laughs] But I used to want be... I had to know this. I'm fine looking into companies that I know about.