This post is useless.. Some excited newbie writes his first thoughts on MongoDB, which you can't gain useful information.
If i want to install MongoDB on Ubuntu, i would use google, first result for "MongoDB ubuntu install" is MongoDB's web site ( http://www.mongodb.org/display/DOCS/Ubuntu+and+Debian+packag... ). I think it would be better to follow these instructions.
The point is : If one wants to be useful for others, he/she should be write about use cases and possible implementations (eg. " our e-commerce solution and how we using mongodb")