Second Life's IP policy reads: "You create it, you own it -- and it's yours to do with as you please." The idea being that users own the Intellectual Property rights to any virtual works that they create in-world. However, a more honest version might read, "You create it, you own it -- as long as you live within our rules". Because in truth, a user can be banned from Second Life, at Linden Lab's discretion -- resulting in the confiscation of any virtual assets that they own, including those that they've created, commissioned or bought. OK, "confiscation" might be the wrong word here (remember we're in unchartered territory) but the reality is that any IP a user owns becomes worthless if their virtual assets are destroyed along with the closure of their user account.
From the Second Life Terms of Service:
Linden Lab retains ownership of the account and related data, regardless of intellectual property rights you may have in content you create or otherwise own.
You agree that even though you may retain certain copyright or other intellectual property rights with respect to Content you create while using the Service, you do not own the account you use to access the Service, nor do you own any data Linden Lab stores on Linden Lab servers (including without limitation any data representing or embodying any or all of your Content). Your intellectual property rights do not confer any rights of access to the Service or any rights to data stored by or on behalf of Linden Lab.
More: ZDNet focus on Second Life