Does anyone know if it is possible to reset your account to "new" status and restart placement? I know that Battle.net offers one free name change; will taking advantage of that have this effect?
Currently there is no way to reset your stats (without buying another copy of Starcraft and creating a new account). To my knowledge there is no plans to add this functionality either.
Blizzard has stated they will reset the ladders from time to time but the exact date when this will occur (one hasn't happened outside of Beta yet) is up to them. Changing your name does not reset your stats.
With that being said, I wouldn't worry to much about your placement matches. If you really did end up where you do not belong (like bronze when you are clearly a diamond player) you will quickly climb the ladder anyway. In the scheme of a serious player (2000+ games) placement matches are just a drop of rain in a lake.