I may get some flack, but I feel that if I have given a person a thank you in person I do not need to follow it up with a note.
If I receive a gift in the mail, I will more likely phone the giver and have a nice conversation when I thank them.
The etiquette of writing thank you notes stems from a time when pen and paper was the primary method of communication, telephone calls especially long distance were frightfully expensive. Now I can call all across Canada with out paying long distance fees. I can call the US for 4 cents a minute.