[underwater]

There may also be liability when you leave the job as you're retaining copies of data that doesn't belong to you.

Not to mention that in the case of a lawsuit you might be required to give access to relevant emails. Mixing personal and professional accounts could quickly get messy.

[bosch]

^^^ This x1000, all of the kids starting businesses and using the cool new thing Google Apps and forwarding it to their personal Gmail account have no concept of this.