One good reason is that Wikipedia was around before Amazon offered web services. Since then, while I'm sure they've added more broadband and servers, I would gu

One good reason is that Wikipedia was around before Amazon offered web services. Since then, while I'm sure they've added more broadband and servers, I would guess that they are not mass-replacing old servers, instead simply adding new ones when they are needed. Being a non-CPU-intensive website, 7-year-old servers are surely adequate in the backend. I would guess that the newer, more powerful servers have a lot of memory and sit up front caching requests, while the older ones act as the database and process infrequent requests like edits. That they are migrating to Ubuntu does not indicate that they are replacing their hardware. Surely they are just installing it on all their servers to make administration easier. If Wikia did not already have a ton of existing machines and if Amazon gave them a bargain rate since they are non-profit, using AWS might make sense. As things exist though, using AWS would surely be less cost-effective.