5% is requiring that they find for instance a sell price of bitcoins of $610, and a buy price of bitcoins of ~ $578 once a day. and that there is enough volume to sell to not cause a tank before its sold. and enough volume to buy to not cause a rise before its bought.
because 5% is a $31.20 price difference once you account for trade fees (based on 60c buy 60c (0.15% per trade))
even if we broke it down to not just 1 buy and sell per day, but lets say 1% profit per trade 5 times a day ($6 profit + same $1.20 fees) means movements of atleast $7.20 need to be held with enough volume to support the price for all investments to transact before it tanks. then buying back in with enough volume to support the buys to ensure they get that $7.20 cheaper price before it rises.
i have personally done this before on a few exchanges. once you start handling more then 10bitcoins prices move, i have played around with 500 coins and seen the price move alot. so saying it is possible and in someways guaranteed... is a lie.
just 20 coins would make the price on either bitstamp or btc-e move $2 in the wrong direction as there is no price support. meaning the 1st coin thy want to sell will b sold at $2 cheaper then the first coin. meaning if they were playing with just 300 bitcoins (not thousands just 300) by the time they have sold all 300 the price would have tanked and would then need to then wait for a further price drop to then have an oppertunity to buy in for their 5% profit.. its unsustainable
and going back to why i think not only the financials are fishy, but the website itself.. i thought i recognized the cheap template they used..
http://bit.coin.je/ use the same cheap template too..
too many things have put the hairs on the back of my neck up, about this website.. i wont shout scam,.. but fishy is definitely a good word for it