When I was growing up Valentine's Day was another of those bizzare American things that came at me through the television and comics pages, along with Thanksgiving and Hallowe'en. Charlie Brown, Little Rascals, Li'l Abner, Pogo, etc. all did this anonymous card and chololate thing. It simply wans't a part of the culture where I lived (Southern Sydney and the west of the state.) Exotic places like Melbourne or Brisbane might have done it, but we didn't.
Until the mid-80's of course. Suddenly Valentine's Day was an Aussie Tradition along with the Stars & Stripes, 4th July and Mom's Apple Pie football, meat pies, BBQs and kangaroos.
Sending a Valentines to me will be met with a bemused smile and "Uh. Thanks." I don't do it for the same reasons I don't do Hallowe'en and Thanksgiving. It was never a part of the culture when I grew up.