I get annoyed whenever people forget things, but I get annoyed when somebody spills their drink on me, and generally appreciate that it's not their fault and help them clean it up. If somebody forgets things over and over again I feel tempted to offer to organise their life for them which is sometimes slightly rude.

I get especially annoyed when I forget things because my entire life is made of mechanisms to stop me forgetting things, which because of fail-brain is my default thing to do with information.