It's an interesting question of web services. If you depend on Amazon for your file storage, big table for your database, yahoo geo, etc then your uptime is fig

It's an interesting question of web services. If you depend on Amazon for your file storage, big table for your database, yahoo geo, etc then your uptime is figure is a product of the uptimes of those services. This means that using 4 services that have a 99.9% SLA actually gives you an approx uptime of 99.6%. It doesn't sound like much as soon as you include something like Twitter you can really see the the whole uptime graph skew.