I was involved in a similar project in Second Life. I say similar. It was the same concept but a database about the avatars rather than people. Here are my thoughts on the idea:
that allows users to enter all their personal information, weight, skin color, eye-color, traits, education level, name/address, etc, or as much as they want, and that stores that information in a central repository for anyone to use.
How many people have signed up to display their private information in a public database? Our studies showed less than 10% of people were willing to have their avatar information collected for this database. Remember this was non-personal facts about the avatar itself and in no way could identify a real life person.*
If you think you can organize a global plan in a week, you are the man. It took weeks to gather a sample set of avatar data from the digital world.
What's the use of this? This is practically useless you say. Not true. There are infinitely many good possibilities for such a program.
...and infinitely many bad ones.
This is a key problem. This means the data is incomplete, and therefore inaccurate. You could only see how many red-headed volunteers lived in the city.
Don't invest anything you are not willing to lose in this project?
*With some work and a hole in security in 2008 it may be possible to link real people to avatars who were registered users at the time of the security breach.