@Vegas:
Many people fail "fostering-101". That's not anything new. To be a good foster, you have to send them on their ways. If you keep the dogs, then you will have too many to be a foster.
It is hard sometimes. After you foster a bagillion basenjis, you look back, and can remember that you had a few that were just exemplary dogs.
Like Mantis says, it takes a lot of effort to be a good foster, and to provide them the socialization that they might need. You need the ability to segregate your house if one doesn't get along with your own dogs. Then, you have to have time for each group individually.
All the comments herein from experienced fosters are consistent with my wife's and my experiences with fostering. We wondered to ourselves the first time how we would not get attached to our fosters.
However, when you remind yourself how your resident Bs own the house, the fact that there are other very deserving families/people who are ready and willing to provide a good home, and also in many cases how the foster B sometimes feels like a 3rd wheel to the resident B's, makes it a bit easier emotionally to let them go to their forever homes when they are ready. Best of all is getting email updates on their new lives with their families and how they are so happy and blessed with each other.
Bottom line:
If you are a clean freak, fostering is not for you.
If you are always pressed for time on other priorities, fostering is not for you.
If you have a hard time managing your own B's behaviors, fostering is not for you.
If one or more of your resident B's are incorrigibly territorial, fostering is not for you.
If any family members do not care for the unique aspects of Bs, fostering is not for your family, because it truly becomes a family affair whether or not it's intended.