Traffic!

Spam might be good for your business. Spam is bad for the business. I use tgp traffic but do not waste time on it. I hate tgp's. If they disappeared tomorrow, I would not shed a tear. I hate insurance companies, but I also have to use them. Affiliate traffic is way, way too expensive. How that ever started is a great mystery. Actually not, but should be. SE is the second best traffic out there and time and attention should be paid to gaining it. My very best traffic I buy from print sources. It lasts forever. Link exchange traffic from similar web sites is awsome as well....and free. The only cost is returning the traffic. Double opt in is a crock of shit. Like someone said, they didn't opt in to your list. My mailing list is hugely profitable and is totally opt in. I nurture it and it converts extremely well because I reward my clients for subscribing.
So, in my world, traffic generation is as much of a function of content as anything else. It might not be your way, Nick. But it is very successful and has legs and quality.