Obviously there's pros and cons. One of the pros being that you're so much more resilient to what goes on around you.
But if you look at open source projects, many are close to perfectly verifically integrated.
There's also a big big difference between relying on someone's code and relying on someone's machines. You can vender code - you, however, rely on particular machines being up and connected to the internet. Machines you don't own and you aren't allowed to audit.
