Script Summary: "Scrubs" people's names so you can take a screenshot without having to edit out the names.
It pretty much does what you want, unless what you want is for it to rename people in an order that makes sense.
How to use:
1. Go to any Facebook page.
2. Use the User Script Command "Scrub Names" by right-clicking the Greasemonkey icon
3. Watch as everyone's names are replaced by a cold, impersonal number
Bugs and caveats:
- Won't work with names that applications produce (e.g. SuperPoke stuff)
- Won't work for names that don't actually link to a profile page
- I didn't really test this that much