WARNING: THIS IS A SCAM!
There's quite a few things fishy about this. While arbitrage does exist and can net you money, you do it between well known exchanges. BTCpromo is not well known and NOT an exchange. If they are selling bitcoins, they should just be buying directly from coinbase or btc-e and cutting out the middleman (you).
Quite a few of the people vouching for this have recent accounts with little karma. It's likely one guy repping his own post and downvoting everyone else. Notice that there are SIX users all created on may 6th of this year, and they are all saying short blurbs about how they "vouch" for this, it's legit, or you can't do chargebacks?
I'd also like to point out this is one of the worse attempts at a scam and easily spotted. ALWAYS look at people wanting your BTC with skepticism and only use well known places.
Better be careful before using any of those kind of stuff ...
And never believe if someone is telling you that you will be able to gain a profit with no risk!
