I only send e-cards now, as I think the money spent on actual cards is ridiculous not to mention the environmental impact. However my husband likes to send a card so his friends still get one. But I run a tight system on that - if they send one back, fine they get one from us next year. First year with no card, their name is put in italics on my list and they get one last chance. If the next year there is no card then they are crossed off the list! No exceptions.
I used to. I had a set Christmas list and I would automatically send to all of them. Then one year when I had a million other things happening I decided I would hold off and only send one back to those who sent to me first.That year I received a whole lot less than usual. I figured they were probably doing the same thing as me. Since then I have done the same thing - hold off and only send return cards - and each year I receive less and less.