We launched a list building project yesterday using a steady source of traffic that should remain constant over the next several months. We're currently using double-opt in and if the rate remains the same will have a 25k double opt-in list in 4 months. Statistically we would have a 100K single opt-in list in the same period of time should we decide to change over.
I know this topic has been beaten to death a little, and I know there are other factors involved, but generally speaking, if you were in our situation what would you do?
The only thing stopping us from using single opt-in is the risk of being blacklisted by ISPs (is that a real risk and what would we have to do to avoid that?)
Also keep in mind that a very high percentage of our single opt-ins would be real email addresses since we are sending a free gift to their email address.
Thanks in advance for your expert advice. You guys really know what you're talking about.