Why are people so rude on facebook?

[Alex]

So a girl I know on facebook had a party on last night. I sent a message today 'didn't see you there but there was this guy at the party who was selling these cool gems and bought one. How did the night go?' yeah sure, it's general but still I thought she would respond. No response. Then another guy I haven't seen for years from my old school met up last night, tells me he would like to chat and that I should drop him a message so I send him a message on facebook with this funny article relating to a conversation we had last night ask him did he get back to his OK? Again 'read' but no response (now 12 hours later). Do you ever just not respond to people you have as friends on facebook when you are online? I don't use chat on facebook often and it's frustrating the hell of me...