How to create better user experience for customers who do not want to create an account

Trust and personal information security are very important issues these days when it comes to online accounts, so it is not unusual for people not wanting to create an account (i.e. provide personal information) when making purchases or requesting information.

So it would seem like most cases when users are forced to do so it is due to a business or technical rather than user requirement.

So the question is: what are the design patterns or techniques that creates a smoother user experience when forcing users to sign up or create an account? Bonus points if these techniques are actually ethical design practices as well!