Lots of good points here and an interesting discussion - but Brendan has the clincher when he writes:-
When I have paid to go into a club I don't expect to see people rehearsing on stage.

So it's all about standards in the end. Everyone performing on a paid venue evening has the obligation to provide a performance that
- is well prepared, rehearsed, delivered and presented.
- engages the audience rather than the written page/electronic media.
- avoids frequent repetition of material.*

Now this does not mean that folk clubs should be intolerant of the young, the beginners, the improvers or the nervous; we all know that clubs are tolerant, almost to the point of being indulgent at times. (The example that Paul gave of his son is a very good one.) In the end, I suppose it is down to comperes/organisers to identify and refuse to put on performers who are guilty of ill-prepared sloppiness, frequent reiteration of the same material and other factors that contribute to poor communication with an audience.



* Jack wrote "you don't do the same number twice in the same year" Funnily enough, Tina keeps a notebook and records the songs that we sing each week as residents at our club - and she insists on just that no repetition rule (not that our audience doesn't change from week to week). Mind you we've been at it for decades and are still learning songs so we have a pretty large repertoire.