When someone is a starting out sometimes having the words can give you the confidence and mean the difference between joining in a session or just doing the choruses. This is obvious, but I believe that you cannot sing a song properly until you have "sung it out" several times without the words. Folk songs are very often stories and your delivery will not be as expressive or easy if part of your attention is focused on reading the words. A friend of mine, a young female singer, has a lovely voice and has won compititions, but she lacks confidence and now she is losing bookings (two to my certain knowledge, possibly three) because she insists on using a song book and sees nothing wrong in this. While I can understand people occasionally using the words it is not good practice and akin to leaving training wheels on a bicycle. Another situation I have started to witness recently is that if I have the words in my pocket I invariably panic and want to get them out, so I usually don't carry them with me, only problem is that at the slightist hesitation several well meaning people shove their words under my nose! This causes me to completly hash up the rest of the song. I have now decided to make sure I learn the blasted things before taking them to sings. (UK and cookieless)