Please create documentation about Data deletion and data retrieve

It would be nice to have any kind of (legal) documentation, that proves what happens after I delete a lead from our database.

• How long the data is still available on Marketo's side?
• What data is stored, and how long on Marketo's side?
• How long can I retrieve the data, if that was deleted by a mistake?
• What data can be retrieved?
• etc.

This would be useful in any situation where Marketo and Customers should prove that the data deletion really happens permanently on Marketo's side, if it's necessary.