GH, nice touch using an image with a partial transparent background to achieve a different shape than most other members. Even little things like that can attract attention to your profile, which is good as clients search for freelancers among hundreds of applicants.
When I went to see the portfolio you wrote about, I was surprised that I could only see your oDesk Community about page and could not locate your oDesk freelancer profile. So did the supposed impostor use you portfolio and photo before you even had a chance to include that data in your own freelancer profile?
PH is correct. Contacting support is probably the best and quickest option. Maybe a Community moderator or manager will read this post and attempt to expedite the issue via support on your behalf. For oDesk Support, please go to the oDesk Help Center https://support.odesk.com/
Edited 01/09/2015 RT/lwm
I am sorry somebody used your portfolio pieces as theirs and thank you very much for contacting oDesk Customer Support. You will need, however, to provide more information in the support ticket you initiated such as a link to the profile where your portfolio pieces are used without your authorization. oDesk Team will take appropriate actions once they review and investigate.