Every once in a while I have to inform somebody that it is necessary to move their signup process to confirmed opt-in (aka double opt-in) to fix a delivery or blacklisting issue. Not everybody wants to do it. Some folks will tell me that they shouldn't have to do it because nobody else in the whole world does it.
Turns out, that's just not true.
I run across lots of sites utilizing COI/DOI as part of their email list signup process. Here's one I ran across today: Cook Brothers, a large discount retail store located here in Chicago. They claim to "Stack em Deep and Sell em Cheap." Not sure if that's true, as I haven't checked the store just yet. But having just signed up for their email list, I can tell you that it does indeed utilize confirmed opt-in. Check it out for yourself.