After an interview, how do you send a "thank you" letter?
Depends on how well we communicated but usually I hand write it.
Depends how they've been communicating with me, I'll respond the same way.
Email might be easier and faster but by hand might be nicer
It makes more of an impression
Email is enough, if at all. Don't seem pushy.
Yup. Typically, I wouldn't even do that (there may be an exception or two). Thank you letters in response to interviews are not currently in fashion.
Violence, why do you say that? Because the interviewer is too busy for formalities?
People have enough in their inbox and enough paper on their desk to actually deal with--stuff that matters--without every interviewee adding to the pile.
If this were a high level interview, or perhaps a second interview with strong prospects, I'd do the thank you note as an email. It would have to be special circumstances for something handwritten.
A hand written card makes more of an impression than an email.
I'm assuming you do send a thank you note, because you really should.