[ge0rg]

The worst offender here is Microsoft, if you have a personal and a business account under the same email address (that alone is a major UX fuckup). But they add insult to injury by showing you a typical email+password form, and when you press [Tab] after the email address and start typing your password, the form is replaced under your eyes with a dialog to choose which account you want to log in, only then followed by a password prompt.