Oh it definitely doesn't make your username 'up for grabs'. What happened to you totally sucks and I hope you manage to get your account back.
That being said if you're not actually going to use your account you might want to at least consider giving it to someone who would put it to more active use. Just a thought.
I've been actively using the account for other purpose than tweeting, and had a vague plan to start using it for tweeting again. Should I have mentioned the plan publicly so that the attacker would have refrained from blackmailing me? I don't think so.
Maybe google.com should have built their web site on kljasdklfjnaksdfn.com instead. That would have worked out just as well for them right? I haven't used the web very much.
That being said if you're not actually going to use your account you might want to at least consider giving it to someone who would put it to more active use. Just a thought.