>* Most early-stage startups use the (in 2008, when I did mine) best practice of “delete=1”. Changing your whole database over to permanent cascade delete is only easy if you’re a very experienced programmer or who knows what he’s doing.*

You do not have to do cascade delete. Just invalidate the data that identifies the user (this includes also transaction dates).

Well, maybe it is possible to cross reference a person based on the transaction volume?