I am so with you on this one! Its actually one of my pet hates, the lack of common courtesy.

I also do the same at the supermarket and I am always surprised by the reactions I get, people are really surprised and thankful.

Yes I let traffic in.. however I dont think its hard to give a little wave to say thanks and acknowledge it! I hate it when people just expect to be let in or just drive out in front so you have to stop.

I also give my parking meter slips to whoever I can see around that has just pulled up, I have even put one back in the machine tray when there wasnt anyone to give it to.. I just hope it made someones day!

People never holds doors anymore, its so rude!! I had some old guy let the door slam in my face when I was carrying DS the other day.. it was obvious I had my hands full!

I could go on... its just one of those things that really irks me!