I remember, quite clearly, doing the math on EMC the first time someone touted it. I was considered "quaint" at the time (dot com boom) for concerning myself with P/E ratios, but I did the math, and figured that they would need to sell everyone on earth a couple hundred megs (lots of space back then) before they could justify that price.

So I passed on buying it.

A month later, the stock had doubled, everyone was talking about it, and I redid the math. Now everyone would need a Gig or so. Sheesh.

So I passed on buying it.

A month LATER, the stock was something ridiculous ($120/share? something like that) and I gave up and followed the herd: I bought in. We all know what happened next: dot com bust. EMC promptly tanked. I rode it all the way down to $15 or so, and finally sold out.

The lesson? Stick to what you know. Warren Buffet is said to have mused "Someone is going to make a lot of money in Tech, but it won't be me" because he knew he didn't know what was going on there. If I'd stuck to my guns (my "quaint" P/E math) and ignored the crowd, I'd've been thousands of dollars ahead.

-Jeff Evarts