In late August/early September, I considered buying stock in Markel Corporation (MKL). I waited for a price of $350, but it never quite got that low, and I didn't want to buy as it kept going up past $380. Four months later, now it's over $480. If it becomes the next Berkshire, and I didn't buy over a 5% difference in price, I'm really going to kick myself. (I did, on the other hand, use that money to buy Berkshire itself with its B-series trading at 310, now at 360+.)

I took profits on half of my Carmax (KMX), whose run-up had taken it to an uncomfortably undiverse 30%+ of my portfolio, and used some of the proceeds to buy shares of AES. I was promptly rewarded by Hugo Chavez confiscating their Venezuelan properties. One would have thought the market already accounted for that in the stock price, but apparently not, and I took a hit.

Similarly, Apple stock goes up $10 just about every MacWorld, even when they're not announcing something as cool as the iPhone. One would expect people to buy before MacWorld, rather than as they're hearing about Jobs's speech, but that somehow never happens. This implies that, should something happen to Warren Buffett's health, Berkshire stock will drop precipitously, even though his death is fairly certain at some point, and that should already be priced into the stock.