When the friendship (privacy) system is revamped, I personally would like calling cards to be retained pretty much 'as they are'.
Unlike friendships - they introduce no feeling that contacts must be reciprocated, and they don't fill your screen with 'spam'. They do however provide a quick and clean index of folks you want to keep track of, or who you wish to keep track of you.
Examples;
I met an individual who was crossing the sims by balloon - and e indicated that e did so on a regular basis. I simply offered eim a calling card, and asked to be called if they wanted company on future flights (which they indicated they did).
I have the calling cards of several builders/texturers whom I've met, and can easily contact them with offers of work.
I have the calling cards of several other builders whose work I admire - and who keep their picks updated with their latest builds and products.
I agree with those who think that the privacy aspects (who can see me when) of the proposed system revamp are important, but lets also consider that their is more to interpersonal contact than immediate communications. A calling card serves as a link to an individuals profile - their 'website' inworld if you will. Let's not confuse a phone directory (your friends list) with your browser bookmarks (your calling card list).