A pretty useful, logical and sensible list. I'd be actually surprised if most SaaS startups were NOT doing this. As a one man show (recently doubled in size to TWO!), I've ticked off nearly everything on here.

One question though - is on the multiple domains bit. Not sure how several separate domains is better than one domain utilising subdomains for API etc.? Intrigued about the 'secret' internal domain thing, and I guess it would apply to larger organisations.

I'd be interested to hear how many startup founders here have a separate internal domain name for back office stuff related to their web offerings.