My good friend Aleister Kronos has just noted in his blog that "The L Word" has just set up a stack of islands in SL, with their own registration route into SL that avoids the standard Linden Orientation Islands. He briefly touches on the potential for this as a more controlled and structured route into SL for business users.
To expand.... what The L Word are using is the Registration API... a tool which enables organisations to offer Sl registration via their own web site. The only caveat is that it is made clear that registering for SL means entering into an agreement with Linden Labs. Once into SL, the user is free to wander where they please. Similarly, the alternate orientation islands are available for other SL residents to visit.
The potential for business users is that they can steer their users away from the hubub of the standard Orientation Islands (which, I noticed the other day, were heaving with newbies..... there is a veritable flood of new useres pouring into SL at present). They can bring users into their serious business applications, before getting distracted with the trivia of flying or furry avatars (see my earlier posts on these topics).
More details on The L World's site, and the custom entry point can be found in the "mynake is kate" blog
On a related tack, I heard recently of organisations with their own private (internally hosted?) areas of SL that were totally hidden from the outside world. I wonder how long it will be before it is possible to buy an SL grid for use behind a corporate firewall, just in the same way that we now have intranets firewalled from the internet??