This mentality should also extend to any sites using the "Like" button...they should all be mentioning that they (and their affiliates) place cookies on your system.

Right from Time's privacy policy:

We use cookies to understand Internet usage and to improve our content, offerings and advertisements. For example, we may use cookies to personalize your experience at our web pages (e.g., to recognize you by name when you return to our site), save your password in password-protected areas and enable you to use shopping carts on our sites. We also may use cookies to offer you products, programs or services. Similarly, as part of an arrangement with our business partners (including, those who present or serve the advertisements that you see on our web pages) we may also access cookies placed by others and allow others to access certain cookies placed by us.

We may also use small pieces of code such as "web beacons" or "clear gifs" to collect anonymous and aggregate advertising metrics, such as counting page views, promotion views or advertising responses. These "web beacons" may be used to deliver cookies that conform to our cookie policy. For more information regarding cookies, please click here.

If you're not cool with that, stop visiting the site or disable your cookies. ;)