>information supplied here will not be retained or used for any purposes outside of delivering your card.

This might actually be purely benevolent, or at least not bad, just your every day cheap marketing project. Some designer's 20% time project that had no reason to not be approved.

That's what I thought too, but on the page they state:

"Cards containing inappropriate content will not be mailed, and information supplied here will not be retained or used for any purposes outside of delivering your card."

Wouldn't they disclose that? Also, if that were the aim, why limit everyone to a single card?

Do companies usually disclose that they're collecting information when they're already, well, collecting it?

But if they weren't going to use it, they would disclose that, and they do: "information supplied here will not be retained or used for any purposes outside of delivering your card"