In this day and age of technology, there seems to me no excuse for standing someone up. You have e-mail, texting, cell phones...surely you can find a way to let someone know what's going on. This especially applies if you've agreed to come to the event you were invited to or agreed to at least let someone know if you're coming or not.
So, if you decide not to come, but fail to notify the person that you're not coming, then you're just being rude. Exceptions to this, of course, include death and unforeseen emergencies. Finding something better to do or getting roped into going furniture shopping with your wife is not an emergency.
