The Japanese sometimes sell BTC Mondays causing 300 USD Bitcoin price drops!
Buying in now is a gamble!
Care to share the source? So that we can determine the information if its legit or not or else this would just turn out to be a FUD and that is what most of us hates especially those people who are easily swayed by these kind of information.
On the contrary, even if they do sell on Mondays, buying is not a gamble because you know when a possible dump might happen so you could play around your bitcoin to earn you profits.
Its barely transparent to all of us who traded bitcoin nowadays, nobody aim for long term profit but rather choose to play day trading. However we couldn't control those group of people who did those kinds of trading strategies, because all of us wanted profit in an instant.