Brett Trout has a post worth reading on "Who Owns Your Website?"  In the post Brett warns clients to carefully read the agreement and to take steps to ensure you own your Website and the domain name.  As Brett says, 

"Most clients think they are obtaining an “assignment” of these things when they write a check. They are shocked to learn that the people they paid to create these things actually still own them. Intellectual property laws are designed to protect the creator, to encourage the creator to create. If you hire someone to design a website for you, what you are actually purchasing is a “license” to use the design for the use intended by you and the designer."

So make sure to read your written agreement with the Web developer and carefully negotiate the terms of ownership of the site before you make any payment and before any work is performed by the developer.  Further, there is really no reason to have the developer obtain your domain name for you.  Just go to www.godaddy.com or some other site to obtain the domain name on your own.  It is easy and if you register it in your own name there won’t be questions about who owns the domain name down the road.

P.S.  I also wanted to give a big shout out to Brett who is speaking at the Blog World Expo.  Brett is talking on keeping your blog out of court. The Expo is November 8 and 9 in Las Vegas.  See the Blog World Expo Blog for information on the conference schedule.  Congratulations on your selection, Brett.