I have had great success by sending out personal invitations. My best response is when I talk to people in person and actually get their email address and send them a personal email invitation. I give everyone I meet a business card. Also, I promote to a lot of people who aren't looking for a business opportunity but want a website. After all, once they sign up for a website and use the website builder, they can access and change their websites and they love that. This is what I am concentrating on now. I tell them that if they refer 10 other people, then basically that will pay for their website and it will be free for them. People who are happy always refer other people.
I also think that using the invitation system isn't as effective because it is tagged as spam, even though it's not spam, and it goes into their bulk mail folder and a lot of people don't even look at it. That is why I send my email out personally from my yahoo email account. I do them one at a time and personalize them so that they don't look like junk mail. It works better. Remember, people can use a website for many things: car clubs, showing pictures of a brand new baby, selling a house, promoting a business, service organizations, soccer teams...the list is endless.
So in other words, if you treat this like a real business and not some type of MLM, and get really professional, and talk to everyone you see about your great website business, the results will eventually come. And so far for me, they have come a lot faster than any of the other MLM's I've tried. I love GDI.

Kris