High Scalability Building bigger, faster, more reliable websites.

I was wondering if it is already possible to scale a MONO's .NET website. I cannot see any real websites (with the term real I mean "a highly visited website") running mono. What do you think?

Will MONO ASP.NET scale???
Is it worth planning a site to run with Mono asp.net? Or should we leave it to the future?

What do you think?