That's exactly one of the tricks.
Party A holds 1M coins and earns a 1% annual PoS "stake."
Party B rents those coins from party A at an equivalent of 3% annual return.
Thus, for a cost of only 0.25% * 51% = 0.000125 of the existing money supply (let's take XMR as an example - that's $525 USD right now), an attacker can mount a 51% attack for a month.
Man, with that kind of opportunity, I should go write some code...
(The other person who asked about subtle attacks: Just don't orphan everyone's blocks all the time or hold up transactions for too long. But you could easily do things like stopping all deposits into an exchange for an hour or two in order to manipulate the price, if you were so inclined...)
Ill admit I misread the question somewhat particularly after entering the conversation after the POS vs POW was in full flow. In regards to renting someones coins I was thinking more in terms of staking for coin profits rather than in regards to 51% on the network.
Continue people
