Does Django scale?
Note that if you're expecting 100K users per day, that are active for hours at a time (meaning max of 20K+ concurrent users), you're going to need A LOT of servers.  SO has ~15,000 registered users, and most of them are probably not active daily.  While the bulk of traffic comes from unregistered users, I'm guessing that very few of them stay on the site more than a couple minutes (i.e. they follow google search results then leave).  
For that volume, expect at least 30 servers ... which is still a rather heavy 1,000 concurrent users per server.
I'm building a web application with Django. The reasons I chose Django were:

I wanted to work with free/open-source tools.
I like Python and feel it's a long-term language, whereas regarding Ruby I wasn't sure, and PHP seemed like a huge hassle to learn.
I'm building a prototype for an idea and wasn't thinking too much about the future. Development speed was the main factor, and I already knew Python.
I knew the migration to Google App Engine would be easier should I choose to do so in the future.
I heard Django was "nice".

Now that I'm getting closer to thinking about publishing my work, I start being concerned about scale. The only information I found about the scaling capabilities of Django is provided by the Django team (I'm not saying anything to disregard them, but this is clearly not objective information...).
My questions:

What's the "largest" site that's built on Django today? (I measure size mostly by user traffic)
Can Django deal with 100,000 users daily, each visiting the site for a couple of hours?
Could a site like Stack Overflow run on Django?