Had a horrible experience of a “dark UX pattern” over Christmas. A yearly subscription was up for renewal. The first reminder was when they tried to automatically take payment, no reminder beforehand. Went to cancel, found out that you can only cancel if you call them. Given it was Christmas the call centres were shut for a few days. They tried again to take payment, it failed, then they sent out an aggressive automated email to say I must pay. Definitely what not to do if you care about users