The Bitcoin wiki mentions it in the article about anonymity (for bitcoin mixing), but i am weary of putting trust in a third party. Is Mybitcoin.com a reputable site, or are there better sites for the purpose of bitcoin anonymization?
If your looking to scamble your coins you could just send them in and take them back out a little at a time to avoid risk if you don't trust them. I don't think I would trust them for anything more than medium term BTC storage (around a month).
For long term I would look for a company that has insurance, that you pay a nominal fee for.