Take this example:
In the past I ran my own business for about 6 years and I've always had up to date business cards. Whenever I met someone exchanging cards was always like a handshake (of course there was always a real handshake to complement the metaphorical one).

Last year I took a job as Lead Web Engineer on a web site linked to a bunch of radio stations. During that time I met a LOT of people from many interesting places (including the head sales manager for Microsoft Australia), as well as many other important business personalties and interesting people (it was a very very interesting job in that regard).

My big regret is that while I worked that job I never had a business card (despite asking for one many times) and it was SO embarrassing talking to these amazing people and not being able to leave them with my contact information.

The end result is that I've met many interesting people (and hopefully left a good impression), I have their card and contact information but they don't have my details!

WHAT AN ANNOYANCE, and potentially missed opportunities.

Very soon I am about to move into another extremely interesting job, and they've made it clear that they're getting me business cards (I am also bound to meet interesting people in this job). In addition I am also considering making some personal business cards to hand to people that I meet, nothing to do with my job, these would be cards with my name, my emailm and my mobile number. I will be doign it to hopefully maintain personal contact with people I meet.

Also, regarding business card sizes and shapes:
WHY DO PEOPLE MAKE STUPID DISFIGURED BUSINESS CARDS?!?!??!
They're so damn annoying!!
I expect each card to confirm to a certain shape so that I can easily store them. I always put mutated business cards outside my main collection because they don't fit when I store them any make my neat stack look out of whack.

Also, concerning size, larger cards are also annoying. Larger cards don't make me think any higher of the contact and they suffer the same problem of not fitting in many business card holders, and hence inevitably being misplaced and lost forever. In that regard smaller cards are better than than bigger cards. Try and stick to standard business card sizes.

I am a fan of light embossing, fancy materials and having nice colour schemes (but not over colouring). IMO making disfigured cards always costs you more money (that could be spent on efficient marketing) and lessens your impact because many toss them aside (and because of my time in business I KNOW that many people share my opinion on mutant business cards. DONT DO IT!)