I was waiting for someone else to respond with your answer Adam. I second his thoughts
A name is something for your eyes, so you don't go blind looking at numbers. I think the number (uid/gid) is your representation to linux as to what user/group it is.
As for the numbers being anything...
It's not going to be a big problem, as long as the uid is not already assigned to something/someone. The main thing on that is that "usually" your users (depending on your distro) are above 500. It doesn't mean that they will acquire super powers, and mind control if you place them lower, it's just that usually the lower numbers are reserved for the non-existent "service" users.
The exception, as noted by Adam, is root's uid, 0.
If you want your computer to have multiple users, but all of them have the same amount of access to each other's files (full access) then I would guess this would be the way to do it. Otherwise, you will probably be better off leaving them as seperate uid's.
This is the same answer as Adam
just expanded a bit more