If desired, the drive can be configured to simply deny access when unauthorized entry is detected. It can also perform a data wipe on the entire drive or specific blocks of information. Other options allow users to delete certain data ranges every power cycle or if the drive receives multiple invalid "Unlock" commands. Based on the press release, it sounds as if the drive performs a cryptographic wipe, deleting the keys required to decrypt protected data and not necessarily scrapping the data itself.
There might be options for both but the effect is the same regardless: nobody's accessing your information. The drive uses AES 256-bit encryption, which the US government has deemed worthy of protecting top secret data. Toshiba hasn't revealed the full specifications of its MKxx61GSYG line, but models will come in capacities of 160GB to 640GB with a 16MB buffer and a 7200RPM spindle speed. Mass production will begin this spring and Toshiba hasn't named any customers or prices.