I guess it depends on your definition of "newsletters that users subscribed to." I have never voluntarily allowed a company to add me to their mailing lists for any reason. I always carefully check or uncheck the appropriate checkboxes so that I don't get added to mailing lists. Yet I've ended up on literally hundreds of mailing lists over the years. Luckily, for these types of cases, where I bought something from a legit company, they honor their unsubscribes. But really, why was I subscribed without my consent in the first place?

What's worse is some places will re-add you to their lists every time you buy from them again. (I'm looking at you Moviefone.com!) I already unsubscribed. Why the @$#% are you re-subscribing me? It's not effective at all. It makes me never want to use your service again, which is what I've done with Moviefone.