If dedi is offline it won't take much till the shared account will overuse it's resources and the host will suspend you. Then you will get a suspended image on ppl's sites. Even more unpro. Better go with a VPS for the backup. Also Amazons s3 will be very expensive as every 1 kb file would be billed as a transfer. Also how will you sync data?
I plan on syncing the data with computer sitting in a spare bedroom. the only thing that will need to sync will be the database which shouldn't be that big. It already runs some maintenance stuff like pulling rss feeds every hour. if the site does failover I will have the backup site not allow write access however read access should remain in tact (the ads will keep serving) I think everyone should know about dns failover though, seem crazy they don't or it's not recommended by hosts (99.9% just give you a box and keep your dns their also) even if you have a single page on the failover machine saying "we are down" it's better than locking everything up or serving a dead screen (twitter, bloglines, adbrite, etc use this method) I never knew how they did it until now
DNS failover is worse than having multiple DNS as it will switch after a few minutes. Multiple nameserver (and servers) would switch instantly. I'm not really sure how you will manage to sync all data (db as well) without eventually corrupting something. Also adbrite and other ad networks run geographicaly diverse clusters to minimize response times (also a bit factor in not slowing down the sites).
It might be hard syncing data on a home connection when the two servers will more then likely be on 100mbit connections, if not more you may corrupt a lot of data like that...
I don't need perfect syncing, just read access that is relatively up to date. No corruption because users won't be writing to the backup, just backing up script will. adbrite goes down also: http://www.flickr.com/photos/laughingsquid/889418039/ I will look up "multiple dns", thanks for the terminology
isn't multiple name server provided with failover? for instance I now have 5 different nameserver addresses for my domain, all with very different c class numbers that dnsmadeasy gave me.