Jim Carroll: "Janie,
... My instinct is to suggest that you sing the songs you know, whether you repeat them or not, ..."

That may be your instinct, Jim, but some of us, as performers and/or as audience members, would rather have more different songs presented than have everything done excellently with no cheat sheets.

Janie's earlier post is an excellent summary of how the disdain for ever using printed material can suppress people's enjoyment of the process of making music.

I would add that some people cannot get by with just overlearning a few dozen songs.   I, for instance, do music professionally for senior communities such as retirement and nursing homes.   To provide entertainment (for some) and music as therapy (for others) for a wide spectrum of communities, I need to have hundreds of different songs that I can and do use for concerts, parties, sing-alongs, and room-to-room music. I probably have at least 500 songs committed to memory - and many others that I can do upon request with only a brief refresher glance at the lyrics.   If I add the repertoire that I use at folk gatherings - which doesn't overlap a lot with what I get paid to play and sing -- that adds another couple hundred.      And many of the songs I do are somewhat seasonal or audience specific, plus my audiences often make requests.   I'm not a great singer or guitarist, but I do have an exceptionally large and eclectic repertoire, which is important in my work.

Again, we're back to the one-size-does-not-fit-all concept.   
Both for most of my paid gigs and for most folk workshops and song circles I attend, the focus is more on enjoying good songs, having people join in, and performing them decently.   And lyric/chord sheets can be very helpful, especially if they're large enough print to be read from several feet away (and at a glance).   

--

Howard: "Folk singing doesn't require a perfect voice, or even very much in the way of performing skills, but it should it least involve singing in tune and remembering the words. "
Just my opinion, but I'd much rather listen to someone with a good voice and impressive instrumental skills who had sheet music on a stand in front of him/her than to a mediocre musician and singer do a song that's been perfectly memorized.
A soloist using sheet music doesn't bother me any more than it does when orchestras or choirs do.




tBut having said that, I still am not convinced that anybody can interpret and enjoy the songs while they are being read from a page, either singer or audience.
But I think the argument here is wider than the situatuion you pose. We are talking about the general use of crib-sheets by people who are able to learn songs, but don't or won't, for one reason or another.