I would propose for the simple commerce module to log all sales, regardless of whether they were done by members or non members: Non members can buy with no problems, but their sales are not counted for the {item_purchases} variable, eg, and PayPals IPN data is not stored.

Moderator’s note: Merged with an existing request.

Not every type of order needs to have the extra step of setting up a member account at a site. An option to track non-site member orders would be great!