Well 2 hosts is a good thing. I use one, but I can imagine, that if you have a real huge program, you wuould use 2 solid hosts.
If you do, I would take 2 hosts that uses different BW(one verio, one level3 for example), or are both multihomed.
BTW look at that host that hosts microsoft, 2 years uptime with not even one minute downtime
Andre