Thank you's go out by email, with a note. Or a phone call. (we don't do a lot of gift giving in this family.). But thank you's are definitely said.
If it is not family, a written note goes out. I sent a thank you note to a local club for a small scholarship. I was very surprised to hear that I was the only one who had ever come into the funding office to get an address to write a thank you note. How ungrateful is that?
My nephews never ever, not once, thanked me for any gift, so I stopped sending them gifts. I've taken them out of my will, too. I figure if they aren't the least bit grateful, they must not want what I am giving and it will go to someone who will appreciate it.
Something to think about for those of you who receive gifts and never thank the sender.