Weak hands are people like MatTheCat, fonzie, and some others who are scared to hold coins for long and when the tree starts shakin' they don't know how fast to dump their coins again. Also people like the ones Blitz referred to who buy some coins to ride the imminent bubble and when they don't see a bubble within 2 weeks they will sell their coins again disappointed. Faalhaas is a perfect example of this.

Then we get to the Veronicas who think they are a strong hand at first, but then get really scared when they see the price drop hard and eventually give in and dump their coins at the bottom or close to it. This is also a weak hand, but one pretending to be strong until tested and these people will naturally suffer the most.

Then we have the day traders who use TA and stuff to try and buy low sell high. They are also weak hands but a small percentage of them are actually good enough to make money from the market. Most of them will miss the biggest profits during the big Bitcoin bull rides though, but they're at least trying to manage their risks.

Then we get to the long term investors who are generally long on Bitcoin, but take profits out during big rallies and they also may buy more when they see dips. These I regard as strong hands with a decent sense of risk management. In terms of time investment and profitability I think this is the most efficient form of trading/investing in Bitcoin and I personally try to stick mostly to this strategy. I admit I do tend to also be a part of the last group, the true superstrong hands who are called the HODLERS of course. Being a HODLER has many advantages like no need to submit yourself to exchange risks and no need to wreck your brain and invest time into deciding when to sell and when to buy back. The disadvantage however is that you may spend a lot of time underwater or lose your entire investment one day if Bitcoin fails. But these people don't care as it's either all or nothing for them, and that's also a perfectly valid strategy if you ask me.