When the 'weak hands' sell they often buy back at a cheaper rate with more coins.
This is most definitely true. Perhaps not for all of them but this 'weak hand' does it often.
Until they get caught in a bear trap... Then they are empty hands.
I know a few people who were selling and buying back cheaper, and managed to make gains for a while. They were doing okay at first, but they got caught off guard when price made a major rally, and ended up buying back in at a loss. Now those guys are currently holding less coins than if they had just held...
Basically I think trading is great if you really know what you are doing and can completely detach yourself from your emotions. But I don't know anyone who can actually do this, so I tend to advise my friends to buy and hold...
There is so much inexperience prevalent in trading bitcoins that it is hard to make a mistake that cannot be corrected in the near term. I've made plenty and all were easily mitigated with fairly mindless corrective trades. Bitcoin is one of the few remaining forgiving markets.