Impolite Text Messaging

Has Texting Changed the Rules?
Has Texting Changed the Rules?
Has Texting Changed the Rules?
I can't help thinking how rude it would be to start a conversation with someone while I'm having one with someone else.  But, it happens all the time.  The only thing missing is the sound of the other voices. I'm talking about texting.  I will be mid conversation, and the other person will look at down, and start typing...