The only thing stopping MongoDB from being a download and run process is the need to create a /data/db. I realize that sounds trivial, but it does trip up some people, and it makes writing "how to get started with mongodb" type stuff slightly less streamlined.

Is there any chance that if /data/db doesn't exist, the mongod process tries to create it? And, if it fails, it spits out a very clear and helpful message which isn't just another line in the log...some ascii spacing to help users:

************************************************************************

• ERROR:
• Failed to created, /data/db. To fix this, you can:
• - Manually create /data/db,
• - Create a different path and launch with the --dbpath PATH option
  *
• For more information see: http://mongodb.org/help/mongodb-fails-to-start
  *
  *************************************************************************