I have thought about it. I once babysat for a couple who took in foster kids. The problem is, the restrictions are so high to become a foster parent that it almost makes it impossible. The last time I looked into it you had to make sure you had X amount of rooms for X amount of people and you had to have people approved if you are going to leave the foster child with someone. It seemed like a lot of hassle when you just want to help someone out.
And while I get they have to be overly careful because these kids have enough issues, I don't want to go out and get a 5 bedroom house so I can foster a child but be unable to work without getting the proper paperwork done to approve an outside childcare provider. I don't know... maybe my research was incorrect!