Not worth it in my eyes to have a 3rd party who can revoke my ability to transact business for any reason and will track and analyze every purchase. I don't care about double warranties, and most stores will take defective items back with a receipt.
If you want your life to be an open book that's up to you. I choose not to do so. It's not possible to have complete privacy of course unless you go live in the woods in a shack someplace, but it's not necessary to leak information like a sieve either. It is still possible to have a modicum of privacy if one excercises some control of the information voluntarily broadcasted.
If you're willing to involve a 3rd party in every transaction and give up what little privacy we still have left for a couple hundred dollars a year in "cash back" and double warranties that's your right - as is mine to decline. Cash is king.