You can't beat a good debate about an important issue! Etiquette aside, I think it's largely a matter or personal taste. I remember watching a college friend make tea by putting milk sugar and hot water into a mug, and dunking the teabag in afterwards, which looked revolting! He explained that this is the only easy way to guage the strength of the tea, and i enjoyed the taste so much, I have continued to use this method from that day to this - 30 years and counting.