Why are a lot of people quitting their jobs and after involving in Google AdSense program? - Because it's great.
Everyone can make money with AdSense by doing a little.
Also a lot of people are making a full time income with a little extra effort.
Making money with Google AdSense is simple.
For this you should have a blog or website that lives for at least 6 month.
And it has your own top level domain name.
Also, your blog must have a good resource of information.
Google don't approve 1 or 2 pages blog or website.
So, your blog or website must have 15 to 20 pages to approve in AdSense.
If you run blog, you must have at least 20 posts before applying for AdSense.
After that you can submit your request to Google for AdSense program.
Once your blog or website has approved, you will be provided some codes of Google ads.
You should past those codes on your blog or website.
You will get paid each time whenever your visitors click on your Google ads.
If you are serious about making money with AdSense, you should be serious your traffic resource.
Traffic is the key point of AdSense earning.
Some common traffic generating keys are:

• Submit articles on some high trafficked article directories with a backlink of your blog.
  
• Participate in online forums.
  Join many forums those related to your blog.
  
• Use search engines for traffic.
  It is a great resource for free traffic.
  Make your content with keyword rich and submit your blog on Google and Yahoo.
  Use SEO tools to improve your page rank.
  Also, submit your blog on blog directories.
  
• You can also use social networking sites to get traffic.
  

Thousands of people are creating blogs just for making money with AdSense.