Maybe you experts can answer this.
Is it possible/legal/sensible to use 2 sets of
nameservers? Say I registered a domain at X and
they provide DNS, then get a host and they provide DNS,
If I use both sets and set the registrars domains info
to point to my site, that would give me geograhically
diverse nameservers...right? Then if eithers nameservers
went down, the other would still catch it. I'm sure it's more
complicated than this...I just got to wondering when I
heard some people complain that their nameservers were
down, but still could get to their site using the IP.
Any insight into this?
:)

I think you would have a big problem trying to register ns.yourdomain.com twice. :D

If they pay for an IP number as well as the domainname, they can always go to the site, because the IP is connected to a specific computer/server. This means that if you have the path to your account on your hosts server, and know the iP to that server you can also access the site using the IP and the path. DNS is really just a way for us humans to remember where our stuff is.;) If the host has the ability he might point all his info to another nameserver, and so if their own nameserver goes down, they have a backup.

OIC.
Well, I figured if it were feasible it woulda already been done. :)
Thanks for helping the hosting-impaired. :D