> Installing [OS X] assumes that you'll always have a fast and reliable Internet connection.

Oh, I know all about that, it can be quite an ordeal. Earlier this summer, I spent a month in rural France for a film shoot. A few days after I arrived, my MacBook Air started acting up, all apps would crash immediately after launch. Ran Apple Hardware Test: bad RAM. I called Apple, they wouldn't send someone out to fix it, I had to bring it to an Apple reseller for repair. Which I did, and it was fixed in three days. However, even in that larger city (Poitiers), their Internet connection was bad. They wouldn't install the OS for me because they knew their Internet connection was unreliable. Afterwards, I tried installing the OS via a WiFi network at a local bar, it took 4 hours and then it failed. I tried a different bar, same story. Eventually, I went to a cyber cafe in an even larger city, where it took 1,5 hours and went through.

OS X’s web downloader should allow for partial downloads, download suspension, and redownloading of specific corrupted blocks. It's great that you don't need a disk or USB drive to install OS X from scratch, but the process still needs work.

I don't understand. What does bad RAM have to do with re-installing OS X?

Also, even if the RAM somehow corrupted the OS, weren't you able to boot into the recovery partition? Or even install it on a USB drive beforehand? https://www.apple.com/osx/recovery/

I always format the internal disk when I send in a computer for hardware repairs. I don’t expect to get the same computer back and I don’t want my data to be out there.

It's worse in iOS. I remember hanging onto an old kindle app version for ages to keep the feature that allowed direct book purchases. The upgrade killed this when I accidentally hit upgrade all one day. The annoying notification did go away though.