You're free to hit "delete" on linkedin, but there's a very high likelihood that it will only mean "hide my profile". Anyone who got your user/pass would probably be able to reinstantiate your account and do anything to it they wanted.

agree; don't just delete, suicidemachine.org

I took the step of markedly decreasing the information on my current legit profile. It includes my name and general title, but no job history. Public disclosures of connections, etc., are highly limited.

Having a fictional LinkedIn account can be amusing.