Two things have happened at work recently that have caused me to think about what is stored in my head.
I've been to a quite a number of meetings, workshops and conferences as part of my job but as yet I've never made such an impression that anyone has asked for my contact details (although to be fair the papers I've published do have my e-mail address on them) and so I've never felt the need to have business cards. Well someone obviously thinks I now know enough that people may want to remember me and so I now have 250 nicely printed business cards that I can hand out. It is also quite strange seeing my title written out on them as I'm only Doctor to the bank to everyone else I'm still just Mr -- having two Doctors in the house would just make sorting the post very confusing!
The second thing that happened kind of defeats the point of having business cards though -- I had to sign a non-disclosure agreement. Of course I can't tell you anything about the agreement not even who it is with or what aspects of my work it will cover. So while I may have interesting things stored away in my head I might not be able to talk about them and hence it is less likely that anyone will want one of my business cards.