Today I hit the new Terms of Server agreement. You can read the thing, if you can stay awake or get the highlights here: Updated Second Life Terms of Service. They tossed in a 2 minute video:
The primary change is the Lab is limiting the purchase of Linden$. You will only be allowed to purchase from the Lab.
I gather that third party exchanges will continue to exist. Since it is possible to transfer Linden$ from avatar to avatar, some other types of markets will continue. But, if you get ripped-off by a third party Linden$ vendor, you are most definitely on your own.