Excellent article Nick!
I think the only point that I might disagree with (and only some of the time, mind you) is the first example you give. I feel like you’re comparing apples and oranges a bit with the examples you provide. Giving the blanket statement of “don’t hide your forms” doesn’t always apply and especially so for a service like Mint that would likely have a much longer onboarding process with much more sensitive information that the user would need to provide than that of Twitter.
If I was a user and a service that tied itself to my bank account immediately asked for that sensitive information, I would likely bounce fairly quickly. Sometimes it takes a brand building a certain amount of confidence with a user for the trade-off of signing up to be justified.
It’s all a matter of use cases. Remember that User Needs + Business Objectives = Product Strategy. Sometimes we as UX designers look for a magic bullet to everything, but not everything applies all the time!