There are three reasons employers will keep hiring (even in the worst economies).

1. Because they encounter challenges their current staff and resources cannot help them overcome.
2. Because they seek opportunities that want to pursue, but their current staff and resources cannot help them achieve.
3. Because their current staff and resources are exhaustable and need to be replaced.

If you can present yourself as a source of solution to the employer's problems and the means to help them achieve their goals, you may become a member of their team.