I'd like to see how someone can agressively buy 51% of the coins 
It'll be much cheaper to buy 500m of equipment to get 51% of the Bitcoin hashrate.
It'll be much cheaper to buy 500m of equipment to get 51% of the Bitcoin hashrate.
I see from the posts that a number of people haven't cottoned on to the core issue.
Step one: with borrowed money, buy 40% of the coins.
Step two: sell all the coins, pay back the loan, banking any profits or covering any loss.
Step three: mount continuous, free, penalty-less attacks for evermore.
51% is the minimum for a statistically-guaranteed success. At 40% success isn't guaranteed but those are terrific odds when you can mount a permanent attack basically for free. The odds get more forbidding at 20%, obviously --- but when paired with infinite free attacks, that's still quite tempting.
That's my understanding of the vulnerability anyway.
Cheers,
Graham
You can't borrow money to buy 40% of a PoS crypto, at least an established PoS crypto like NXT, it would be in the range of hundreds of billions (that's with nine 0's) of $$$. Buying 1% of NXTs drives price 25% in geometrical progression. Please do your maths homework first.
On the other hand it only takes hundreds of millions of $$$ to hijack a PoW crypto like Bitcoin, not to mention smaller ones.
Which adds up to, it takes on the range of 1000 times more money to attack a PoS crypto than a PoW crypto.