Business card for Ph.D. student - what should be included?
My experience of business cards in academia is that they are mostly just an easier way to share contact information than scribbling it on a napkin.

As such, the only things that are really important are institution, name, title (because everybody will expect it), and sets of preferred contact information.

As such, if you want people calling you, put down your phone number; if you don't want people calling you, don't put it down.  Likewise for all of the other standard aspects.  You probably should have a web page that you want people to visit.

As for social media sites like LinkedIn: I'm rather dubious about them, simply because there are potentially so many.  I think one wouldn't be a problem, but the extrapolator in my mind goes to a ridiculous image of somebody handing me a card with their LinkedIn, Twitter, Google+, ResearchGate, Facebook, etc.  Don't be that person, or else if I meet you at a conference and you hand me your card, I may have a difficult time avoiding laughter.