Newb question about player content

Hey,

I am trying to get my  head around the concept of player content in SL.

One major difference from a traditional MMO is the lack of resources. Content is designed and created by players without use or transport of resources (correct?), so there is no resource-based economy.

There also does not appear to be a traditional MMO marketplace, where I can buy a costly item and later resell it. At least I don't see that happen?

For instance, if I create an uber flashy shoe, can I just create as many of them as I want?

Horsebreeding seems to be one exception, as I see an actual market for buying and selling rare horses. However since the whole horse industry (e.g. Amaretto horses) is player driven, the attributes of the horses are subject to changes made from the mother company Amaretto (?).

So here is my question then: what if Amaretto the company stopped their business, will all the horses you own simply disappear from the game? What about all the money that players had spend to buy horses?

In contrast, if I disappear from the game, I don't expect that the shoes I created will disappear.

So please help me understand the logic of how this works, thx.