It happens a lot more than you probably notice. The cashier asks for your zip while they ring up your purchase. Something you Googled yesterday is now serving you ads on Facebook today. You get offers in the mail of things you’re interested in, but have never shopped around for. If you think retailers have a lot of information about you and what your buying preferences are…you’d be right.

As consumers, we make a sort of deal with data. We’re willing to hand out a certain amount of data to make information about products and services we’re interested in, as well as specials and discounts, readily and easily available. But are we really aware of the extent and amount of data we’re handing over as we complete transactions and spend time on the web?

And what is the acceptable limit?

Where is the line between, “It feels like this retailer really gets me,” and “It feels like someone is spying on me?”

The new very personalized ads—like the ones from Spotify, Netflix, and World Market—which seemed funny and clever last year are ruffling some feathers now, bringing up questions of invasion of privacy.

These ads raise a murky, gray fog of questions about the depth of data and how it should be used in marketing:

Are the ads quirky and relatable, allowing the brands to connect on a deeper level with their consumers? Or are they too Big Brother-ish for consumers to feel comfortable?

What are these companies’ responsibilities in regards to the data they collect? If they’re not using actual personally identifiable information (without permission), is it all fair game?

How liable are consumers, with their often lassiez-faire attitude about information-sharing?

Why was Spotify’s marketing campaign singling out users’ habits considered funny and positive, when Netflix’s very similar campaign was flayed by the public?

We don’t have all the answers, and this is an area we’ll be probably be wading through till the end of time, but one thing’s for sure:

We really oughta read those Terms and Conditions.

Check out Adweek’s thoughts on this topic here.