Another way of looking at it:
Microsoft ask Goldman to sell some of their shares for them on the market. Goldman obliges and buys the shares from Microsoft for x dollars offers them on the market for x+4 (offer) - and probably x+2 (bid). so either way, they're making money.
you come along and buy a few Microsoft shares and because Microsoft is such a good company working really hard at increasing it's value to shareholders, the price goes up. so both you and Goldman 'win'. but this is not enough for Goldman, so they get their proprietary traders to go after the cash (they used to be able to do that before they sold the shares to you but it's illegal now). so they chase up the price by buying up other Microsoft shares on the market after they have sold them to you - which is great in the beginning. this gets other traders and retail traders jumping on board because the price is going up. then, when Goldman is satisfied for whatever reason, they sell (while people are still buying) and make a killing dumping all their shares. suddenly the price starts falling, people panic and sell and short sellers (probably Goldman again) then jump in and start pushing the price down even further to the point that eventually you who bought in the beginning are also forced out. once Goldman have made another killing, they offer the shares back to the market again. and so the cycle continues. meanwhile, you the retail trader, are sitting on the sidelines dazed and punch drunk from the ordeal and wondering wtf just happened.
moral of the story - if Goldman wasn't such a greedy *******, you would have been fine, they would have been fine and everyone else would probably be ok too - as long as Microsoft pulled their weight and you hadn't bought shares in Fan or Fred.
so basically, if it weren't for the greed of the market makers and short sellers (the carrion feeders) and the subsequent fear of them, the markets would be a very different place...