The LA Times has an interesting article on businesses closing up shop inside the virtual world Second Life.

For a while it just was hip to create a presence in Second Life. We have seen tons of companies and even embassies open up virtual representations in Second Life. The value of just being associated with Second Life has faded. Now it is about actually having a measurable return on investment as with all marketing and sales activities. Most corporate installations are apparently deserted, but red-light districts are packed.
Additionally there are more virtual worlds and social networks that companies can choose to expand too.

For me Second Life did not have any appeal as it is not better than the first virtual worlds that hit the net 10 years ago. Sony's Playstation Home appeals to me more on first glance as it drastically increases the graphics quality and interactivity of the virtual world.