Large Group Monetization

What is the boards thoughts on monetizing large groups (500k+) of generic subscribers?

I've got a group method that could easily clear 500k members (with about 2m being a very real possibility.) However with generic targeting, IMO it might be hard to monetize.

I was thinking of getting everyone to opt into a email list, that way I could have more data on them , however mailing them would be extremely hard as I don't know how to process 500k optins then autoresponse emails + approximately a few mails per week to each subscriber.

Any helps or thoughts would be appreciated.

This is kind of an elaborate, outside the box idea, but here goes.

Find a generic CPA offer say, win an iPhone, and then iFrame it. Above the iFramed offer, write something that pertains to your group, and say "if you fill this offer in you'll get bla bla bla".

Make a post on groups page, detailing that if they fill in this quick win an iPhone offer they'll get whatever you wrote above the iFramed offer. Ensure that what you're pretending to offer them is worth the quick email submit, and is interesting enough to turn heads.

If people begin replying saying they didn't receive whatever you offered, say that it will be emailed after 48 hours or something, just so that you can cover up.

Hope this gives you some kind of an idea.