For a number of reasons, I've had to change hosts once in a while, but I tend to maintain accounts even when I move a domain away from a host.
So, basically, I'll keep two identical sites on different hosts, so if there's a problem with the one that's pointed to via nameserver I can easily switch over.
But it occurs to me that this might be a bad idea in terms of duplicate content, even though theoretically the old site isn't available via its domain name. Typically I use shared servers, without dedicated IP's, but is it possible Google will access both sites in spidering and penalize?
If so, what's the fix? Somehow secure the site I'm not presently using from google?