RoR for a Large Scale App?

I've seen discussion on this topic in the past, and was wondering what
people's feelings were in regards to the more recent releases?
Mainly, could it be possible to build a web application on the scale
of, say, Amazon, or deal with similar bandwidth and load requirements
as an iTunes would? It may be unfair to expect that much, seeing as
these are some of the largest around, but would a setup of RoR scale
to handle this and, if not, what are the limitations that prevent it
from handling it?

Basically, I'm about to embark upon a large scale project and am
weighing my options, and the small amounts of RoR I've developed with
I've loved -- yet I just don't know how far it can go. Thanks for the
input.