As I have said before I am Much more embarrassed at forgetting the words than of having "the book" in front of me, and if you want embarrassement at its maximum, it is in forgetting a song YOU WROTE!!!,(this also applies to songs where you know more than one version i.e. Spanish Ladies and Girls of Tachuano) the trouble often is your brain switches back to an earlier revision (or version) before the "Final" draft and you go down a blind alley that you later rejected and get hopelessley lost!!! But, in the end, it is personal taste and it is the act of Singing that counts, and if more are encouraged to sing by using "the book" then that has my vote. Personally, I prefer to sing from memory but it is not always possible for a variety of reasons (lousy memory, singing too infrequently etc) or a "New song". but I would rather sing, book and all, than not.
"Let every man so bend his song
to help his neighbour sing along
let each and all contentment bring
when Old Men sing"