"Wow. I’m the author of Big Brother – the first web-based system and network monitor… still just C and some scripts… that level of complexity scares the crap out of me!"

Big Brother is pretty cool. I remember using it long ago too :)

I certainly respect the simplicity of BigBrother, but the scopes of the products are completely different. Rackspace Cloud Monitoring is a SaaS built with the ability to be used by hundreds of thousands of unique customers, monitoring millions of 'things'. It also has a goal of never losing the trust of our users -- user's generally don't care if your data center is having a bad day, but they certainly do care if you didn't alert them when their site is down, and so multi-region durability gets added to a requirement list.

Complexity does come from these kind of requirements.