Maybe it would be alphabetical. It's a good question. It's going to be up to the companies to figure that out. They don't care who you are. They just care that you're reading content related to a product.
People are, in essence, doing their own profiling.
It allows the companies to build a relationship with the consumer, who will likely willingly provide more personal information the more trust a company builds. I don't see any downside to it. But that's a really simple task. In the end it will really help you sell well, your 'customers' will be happy, and it's a wonderful revenue source. It wouldn't take long for you to make back the startup fee.