"Why is a fake name better than being a guest ?"

well, just imagine 479 different 'guests' all trying to refer to each other's posts "dear Guest who posted at 11:30 on the 14th"....and besides, true or not, consistently posting as guest leaves a feeling that you have issues with US as listeners. Imagine also going to a party and encountering someone with a bag over their head and a disguised voice and trying to carry on a discussion with them.

if there are REAL reasons to sometimes not use a member name, then call yourself "rumplestiltskin" as a temporary thing..or "old Sam"...whatever...