Hmm, I guess I'll dive into this. I have mixed feelings about this thread. On the one hand, it is hilarious. On the other, though, it smells a bit of folk-crowd literati. As several people have mentioned, many of the songs that people have mentioned are on the list because they show up so often, not because they are intrinsically bad songs. So some people must be voting with their ears. I am reluctant (very reluctant) to object to pretty much any song in the same way that I am reluctant to object to pretty much any book. There are many songs I don't play or sing or listen to, just as there are many books that I don't read, but I object strongly to banning books (even Madison County, Bridges thereof). Similarly, I find it difficult to object to other peoples' taste in music.
Part of the reason I am having this reaction is that I am going off to an annual camp that we have organized with my daughter's school class for the last four years. We have dinner, and then sit around a campfire and sing songs and beat at guitars. Some of these people I see every week; some I see once a year. We end up singing songs that most of us know, including many (most?) of the songs on the outre' list. We sing them not because they are great music, although some of them actually are wonderful songs, but because most of us know the tunes, the words, and can guess at the chords. While part of me wants to view the campfire as an opportunity to introduce wonderful unknown songs to a new audience, the greater part of me justs wants this to be a comfortable evening singing songs with a group of nice people. While I will probably try to play a wonderful Stan Rogers song that no one else has ever heard, along with the standards, I suspect that I will get no more than a grudging listen, because what people there really want to do is sing together, rather than listen to me show off what I have learned in the last year.
Some of the comments about "Rise up singing" jump out in this context. I don't use the book much when I am playing at home. Instead, I use books that have music and songs that I don't already know. But I leave those books at home for campfires and take a couple of copies of RUS, because I know that we will find some songs that we know how to sing and because there will be just enough chords that people who only play a few times a year can play too. Intrinsically, I suppose it's not good music, certainly I wouldn't record it. But, extrinsically it is very good music, because we can all slide into it easily without having to spend all our time worrying about teaching each other words and phrasing.
I think that part of the point, for me, is that music is as much about a social context and a social language as it is about a particular tune and a set of words. Over time, some songs beccome part of a common language. I suspect that there are many reasons why a song becomes invasive, whether it is a catchy tune, a memorable set of phrases, or a particular link to a time and society that people care about for whatever reason. Dylan is probably a good example ("Don't think twice"). There are a bunch of links there: to the 60s, with both the positive and negative aspects of those 10-15 years, a good tune, and an easily remembered verse. I play "Don't think twice" sometimes, other times stop myself because I don't like the sentiments (I have the same reaction to much of the blues). But I wouldn't ditch the song or tell someone else not to sing it. If I hear it on the radio and it bothers me, I switch stations. If I am with a group of people and someone sings it, I'll either wait for the next song or find another group of people if there are too many songs I don't like.
Perhaps another part of the point is that some songs are a form of comfort food, like pasta. I sing "Michael" almost every night to my kids. Have done so for years. By now they both know the words and know that I sing it badly. But it is part of the ritual of going to sleep. While I could get very tired of the song if I heard it in public a lot, I suppose, I don't get tired of it at home.
I am somewhat apologetic about the tone and length of this post. As I said, I think the thread is hilarious. But I don't want us to become too diverted from what I think is our reasonably shared understanding about music, which is that people sing songs and listen to songs that mean something to them. That really is the power of music. So if a bunch of people seem to find something meaningful in a song that I am really tired of, or never got the point of in the first place, I am willing to believe that they must find something that I don't and leave it at that.