Question:
I already have a blog so why would I spend my valued time submitting content on your site when I can earn AdSense money with my own blog(s)?
Also, having my original content on several places will make my blog rank less on Google search results, what can you say about this?

Answer:
The way to go with ad revenue sharing programs is don’t be afraid of copying and pasting your own content, from your blog.
No it will not be seen by google search as a duplicate content since the websites are very different, and on each ad revenue sharing programs you can put links back to the original source: your blog, which should stay the central place of your self on the web, the place where new readers you get from contributing in other websites will know they can get the latest content from your blog directly. So for example you write something new on your blog, wait some days before going through all ad revenue sharing programs and paste it there with a link to your original post.

This should not be seen as temporary and quick way to make additionnal adsense money, rather as another source of income that needs to be built in the same way as you build your own blog. And contributing content will not take long time at all, just login, add content, be gone.

Why do you need to give it time? Because it will take time to get your content on google, msn, yahoo search engines on senserely, on writingup, on bloggerparty, etc.
Join many such websites, put them in a bookmark folder in firefox, have firefox remember the login and passwords. When you want to send content, simply click on the folder with the mousewheel button to open all sites in tabs and start pasting your content, it would take 5 minutes maximum to contribute one piece of content to half a dozen such websites. And the rewards in adsense will be good not tomorrow, not in one month maybe, but think about it in 6 months when you will have so much content everywhere with your adsense working on each of them and every pages linking to your own blog!

That’s the way you should think of it, I don’t know if I’ve convinced you, but at least I’d have tried. :-)