Annoys me more than anything

I have very few pet peeves. The one that gets on my nerves the most is being ignored. I can't tell you how much it angers me to go out of my way to contact someone (make plans, just say hello, etc) and get absolutely NO response at all. I understand a delayed email response. Not everyone accesses their email on a daily basis. But when I leave phone messages or send texts when I KNOW that someone's phone gets texts and they're not returned... I'm not vain enough to think that someone should stop what they're doing to respond to me but when days go by and I hear nothing, it pisses me off like no other. Let's just say that I now realize who my friends are.