Mail Manners

Whether one has any intention of acting on information in an email or not, how difficult is it to fire a quick reply at least acknowledging receipt? I get that people are busy, but surely that was supposed to be one of the benefits of email - that they were quick and easy. No real writing involved, no posting or searching for someone's in-tray in which to drop a printed note. Automated responses stating something has been read don't really cut it either. I have a friend who clicks open every email she gets from colleagues which then triggers the 'read' email being sent back. Has she read them? Has she hell! But here I am, not even an automated response in my inbox, not a brief, 'thanks but I haven't the time to deal with it' or even 'thanks but no thanks' - simply nothing. I feel I wouldn't get far if I played like that.