It’s ridiculous there’s a couple different formats for eBooks, and none of the eBook readers sync with each other. Free and legal *.mobi books you got from elsewhere don’t sync on the Kindle. Having Kindle, Google Books, and iBook on the same device just doesn’t make sense at all. It’d be great if there was a reader that read the different formats, and then used Dropbox API to sync.
In addition, there’s no precieved value add of one over the other. It’s just lock in. And as a user, it sucks.