Double opt in list building

With the passage of the can Spam act I have to question whether it's worthwhile to even consider building a list that isn't double opt in.

However there is no denying that a single opt in list will get you a whole bunch of new subscribers faster and easier than double opt in. The numbers I hear are approximately 20 to 40% more subscribers.

I think that probably depends on whether you have a relationship with the subscriber or not. If the subscriber's is on your list and you've done it right and build a good relationship and maybe don't need the double opt in.