As much as I like my singer-songwriters, I have to agree with Ruth on how folky the Cambridge Folk Festival is. It's not just the line-up, but also how the music is presented. Vast marquees with rock-style sound quality don't really favour folk.
Also, to me, a folk festival has to have a participatory element in it, but Cambridge just doesn't have that. The campsite has some stuff happening, but the festival site itself is a participatory desert.
It'd also be nice if the festival had some involvement with where it's based, but I lived in Cambridge for 3 years before I found where the festival was. The festival is simply irrelevant to the area. Aliens could teleport the entire site to Milton Keynes, and no-one would ever notice until the visitors got in their cars to go home.
And finally, it'd be nice if the festival organisers could figure out how to sell tickets. This has been a total clusterfuck for years, and they still haven't worked it out. If I could order a ticket for this like I'd order a ticket for any other festival, maybe I'd go - there are some people I wouldn't mind seeing (notably Joan Armatrading). But the ticket sales fiasco is such that I just don't see the point of trying.