There are few full-time collectors in these islands, I know of only one. He regards his job as to collect everything he is given, and that is what he is paid to do (though I have seen him introduce a little discretion on occasion). When he did this it was largely due to the pressure he was under (he took us out with him several times in the early-mid 70s). Even then, when there were many more singers about (Ireland) he described his job as 'a race with the undertaker'.
Those of us who collected in our spare time did not have the luxury of recording everything, had to make choices. While we never refused a song we were offered, we tended to steer our work towards those we considered important. This was no great problem as the singers we met, certainly those with a substantial repertoires of traditional songs tended to catergorise them for themselves. Walter Pardon was separating his songs into folk, music hall and popular songs as early as 1948 in his notebooks.
I agree with you entirely about acrimony-free discussion Cap'n, though I suggest you will achieve this goal by not introducing red-herrings such as categoration v performance; the two are not connected unless you wish to make them so.
Jim Carroll