the decision will depend on the person itself ,when even etiquette
rules can suggest its not necessary,logic,education,manners and
common sense,tells me is the right thing to do,even its a multi-corporation,or a small business,show your appreciation is some
gesture that is always welcome,independently if is a thank you note,a greeting card,personally said it,e-mailed or telephone call,
and the best is,you feel great about it!!!