While talking to my peers in the recruiting business, a discussion on thank you notes came up.  The majority of my peers find it acceptable to be sent a thank you email.  As a matter of fact, some hiring managers will base a hiring decision on receiving a thank you or not.  A hand written card is still considered the best form of thank you, but not far behind is an email thank you.  So ask for the interviewers business card, go home, get on the computer and type something nice. You may just get the job for your efforts:)