So much more evil than what CC companies already do today, amirite?

Yes. CC companies are their own silo. Google aggregates data across multiple sources, and you can be certain that you'll start seeing ads related to purchases you've already made in meatspace.

While true, CC companies sell our data to other aggregators. So it's just adding in profit to a middleman while google is doing it themselves.

Is that true? It sounds like a crazy privacy issue, so I would be surprised. But maybe I am too naive.

Oh nice, so the ads will be for things I'm actually likely to be interested in instead of random things I don't and will never care about?

The same argument could be made for an advertiser peeking into your windows at night and watching you in your spare time. Eventually you have to draw the line.

Only if said advertiser is also my butler, cleaning my windows and waiting on me hand and foot.

This is a terrible analogy.

Yes, considering that CC companies have that information by the nature of the service they provide to you, their customer. On the other hand, Google seems to be expanding into more services to hungrily learn more about you and then provide than information to their real customers, the advertisers.

Edit: I should mention that I know that credit card companies sell data to third parties. But they don't exist only for that purpose, like Google nowadays. Thus, people are understandably less comfortable with Google knowing things.

One could argue that the credit card companies are more entitled to my purchase history as they are the ones providing the line of credit. Google is simply doing a user allowed MITM "attack" in this case.