It does seem odd that Netflix isn't consistently displaying the banner ad for the show to all users on the website. That's a definite fail. I can't recall if a trailer space like Bob mentioned was visible in the Netflix app on my Xbox at any time in the past, but I haven't seen any special notice about the show today when I've looked.
Netflix on my PS3 had a banner ad for "House of Cards" about 3 weeks ago, but it only showed up once. Pretty poor advertising strategy if you ask me.