> I don't recall ever getting out my credit card and paying $5 for something from a random link on Twitter.

The other issues with this site aside, affiliate programs don't require the user purchase the item that brought them to the site. There's a book I found myself recommending quite often, so I created an affiliate account at a retailer and started using that link when I recommended it online. I make about $100 each quarter off of site referrals, but almost no one buys the book -- instead they follow the link, click on something in a related items carousel and buy one of those items. Sometimes the time between click and purchase is pretty long (weeks or even months), but as long as the affiliate cook persists I get a percentage of the purchase price.