Basically, months ago i received an evening wedding reception invitation from a guy who i am acquainted with (we both are into our music and wrote a track together too). I was quite surprised to receive the invitation because i would have not really considered myself to be a "friend", more like someone that he knows really. We have done things socially together, i.e. as a foursome with our respective partners etc but i wouldn't have said we were close. So anyway, when i received the invitation i was quite touched that he thought to invite me! I immediately sent back an RSVP to say that yes, we would be attending.
Anyway, the day of the wedding arrives and DS and I go along to the wedding reception. I spot the bride, go over and say hello, you look lovely etc etc. After about an hour, i finally see the groom so went over to say hello and offer my congrats. He sees me and says "heeeeey!! Hello RG, how are you?!. Erm... did i invite you?"
He then made light of his comment by saying that he'd forgotten who he'd invited but i got the impression he was back peddling a bit.... 
I was a bit put out by this comment,to say the least! It made me feel that all the effort i'd put into buying a card and present (albeit nothing expensive) was just wasted and i needn't have bothered going at all as clearly i wouldn't have been missed!
I've never been married so i haven't experienced first hand all the stress of arranging a wedding etc but surely you would know who you invited, wouldn't you?