I can see where you are coming from Gary. But, business cards are your companies calling card. I don't hand mine out to doodle on. The card has everything they need to know. If they need to know more, the site name has all my contact details or, just remember it. Plus, as they are mini billboards, 2 sides are better than one. Why not make full use of the card as, again, that is it's soul purpose - advertisement and reference.
When they see them the first think how cool and secondly pocket and hold on to them. They don't break, won't bend, tear or blow away in the wind and are clear and easy to read. It shows what my business/registry is about within seconds of them holding it and viewing the card. Cardboard is fine too, not saying it isn't but for me anyhow, I like to have the best and spare no expense in getting it.