Why is there a need for Mono? (version 0.1)

We were given a task to pick a technique an explain it in the course Design of complex systems.

I choose the subject Why is there a need for Mono?

An article is available at: http://static.olalindberg.com/wp/2005/051003_ola_lindberg_mono.pdf

Update:  This article was voted, by the people attending this course, to be one of the 3 best in this task