Most of the events I attend in Second Life, including Metaversed events, are not targeted in any way other than implicitly through the content of the event itself. There are no qualifications necessary for entry. We seem content with quantity over quality, which is perfectly natural in a new medium I think. There are surely exceptions to this observation, and I'd love to hear about them.
On the web, provided your content is free of course, there's little need to pre-qualify visitors. Bandwidth is cheap(ish) and hardware costs negligible for many businesses. In Second Life, and other virtual worlds though, there is a limit on how many people can participate in your live event, or visit your server at any one time. There is also a limit on a company's human resources. We talk about engagement a lot when we speak of virtual worlds. About how it's better to engage meaningfully with 10 people than broadcast at 100, or 1000. So why are we not doing that?
Barriers
A good argument against trying to qualify visitors is that it puts a barrier between them and your content. Why would you want to make someone intent on visiting you jump through a hoop?
The other half of the problem may be that if you do decide that you need to pre-qualify, as far as I'm aware, the tools just don't exist. Right now, it would take considerable development to setup even an automated way of managing an islands access list. There are certainly no simple tools available for this. Do correct me if I'm wrong!
Hoop Jumpers
How much more likely are you to have a meaningful conversation with someone that's shown intent, and has been pre-qualitied over someone who wandered in randomly? If you're focused on learning in Second Life, and don't have a clear financial goal it may not make any sense to do any of this stuff. On the other hand, if you do have a clear goal for your presence, and a clear target group to aim at, wouldn't it make sense to spend less time on "everybody", and more time on the hoop jumpers?
In sales, it's preferable to be talking with somebody who wants to buy your product, rather than trying to persuade somebody that doesn't. Isn't it the same here?