Anyone who has played Diablo 2 recently will welcome this, currently you get spammed 1000x a second by item sellers, which sucks. This is a trade system not a buying from the company itself. People who want to buy items will anyway, whether through blizzard or a 3rd party, this way at least its controlled and people wont get scammed. Also gives a chance for a regular player to make a bit of money, I am all for this and think it is a great idea.
D3 wil still be a action rpg, not a mmo. That is nothing to fear.
But blizzard really know how to make money, and income for blizzard is the reason you can pay real money for gear.
Everyone can play it like they did D2 multiplayer(no offline play in d3), so you dont have to spend money.
But there are some people that will spend real money for gear, and no one in the west will ever become a pro D3 loot grinder.
You as a normal player will not have much left for finding even good gear, first off all if you want to sell for money you need a subscription, then you need to pay a one time fee to post an item to the trader, then when you sell the item blizzard will take a %-of the selling price. The money can now be used in the blizzard store "for free" or by paying another fee you can transfer the money to your account...