My company uses TouchDown (in our case combined with MobileIron, but I honestly think this is a HUGE mistake).
TouchDown basically creates a secure bubble within Android that your company's Outlook administrator can manage. They can set heavy password requirements, require encryption, periodic password changes, remote wipe, yadda yadda yadda. All of those policies apply to the TouchDown application only.
You leave the company or lose your phone, you contact the company and your outlook administrator emails a wipe code to TouchDown. TouchDown goes nuclear on its data store (similar to the way BlackBerry works) and all corporate data is off the phone. In the meantime, every attachment you save is saved encrypted on the SD card and is unreadable except from within the TouchDown app.
It's like having a little BlackBerry sit inside your Android.
You can then decide what you want to do with your PERSONAL data in terms of protection, since that's outside the TouchDown bubble. Run it naked, use a PIN, or a full-on password. Your choice.
Combining it with MobileIron means that you need to unlock the phone any time you want to use the phone, and that means that ALL the time you are using the phone, TouchDown is in a less secure state, since TouchDown does not have its own independent password.