Possessive families

I was just browsing through random blogs, and people really don't know when or how to use an apostrophe with a last name, do they? It isn't the Hanson's. It's the Hansons! Unless it's the Hanson's blog. Or the Hanson's Christmas card. But please don't sign your Christmas card "Love, the Hanson's." (Especially if your last name isn't Hanson.) An apostrophe "s" is possessive. There. I feel a little better now.