This has been a pet peeve topic of mine and you are ABSOLUTELY RIGHT that it's dumb to just buy and hold if you don't have to. If you are able to sit and watch the market at any time, it is just a really BAD strategy to just hold no matter what. Risk and reward changes by the second and sometimes it's obvious you should sell (or buy back).
The most glaring example is the bubble run up to $230. It peaked and then slowly dropped from there over many hours and if you were sitting there watching it, it would be crazy not to sell. It pretty much dropped in a straight line down over $100 in value.
This is sort of like saying if you're the best poker player in the world, you should never turn down an option to play against the worst for your whole bankroll. Most people aren't that person, though, and even the best get unlucky.
Yes, there are good day traders, just as there are good poker players, and some of these consistently make a profit. However, when you're basically betting on hour-to-hour price shifts, and frequently buying and selling, you don't just have to beat the market. You have to beat the combined transaction fees from the exchanges as well. You don't just have to be better than the market, you have to be better than the market plus a constant stream of transaction fees.
This is basically the definition of a negative-sum game. While those who make infrequent but large transactions also pay fees, they are basically negligible in comparison to the size of the transaction. When you day trade, this overhead or "rake" becomes exorbitant. While you only have to be reasonably intelligent to make money in the mid-term or long-term dealing in Bitcoin, which is likely to increase in value for the foreseeable future, you have to be way ahead of the curve to expect to profit as a day-trader.
I sold out some at $170 or so, when the price was spiking, and felt mildly foolish when it went to $266. But if I'd waited for the peak, I probably wouldn't have even been able to sell when it started crashing, because most of the exchanges suspended trading or were simply too incompetent to maintain their operations with heavy trading (MtGox I'm looking at you). There was a frenzy of panicked idiots basically trading blind with no reliable ticker value for the commodity.
Note, this is a problem you don't even see in normal day trading, but has happened during both major bubbles because the idiots running the exchanges are basically amateur hour assholes.
I think in the current situation, being very cautious is better than trying to eke out every last cent of expected value, unless you are the best of the best at day-trading (with BTC this can basically be hour-trading or even minute-trading). The vast majority of people aren't.
Those who are here and asking for advice almost certainly aren't. If they were, they wouldn't even care about our opinions.