We would love this feature. We support both partners and end users. We do not want end users being created as a contact as we don’t want them to recieve any of our marketing emails, product updates email, or newsletters that are intended for our partners. As of now, we’ve been told we need to set up filters/workflows/special fields - workarounds that are not ideal.
And reading the above comment makes me very nervous about spam email addresses being created as contacts as well - eek!