Thanks for all the informative replies.
QUOTE(Flossie @ Feb 20 2009, 07:00 PM)

Some people are taught vibrato very early (grade 5 ish) and do vibrato for absolutely everything - this is often at the expense of tone development. I personally don't like this and feel that whether vibrato is appropriate depends on the piece. In my view, vibrato should simply be one tool in tone colouring and should always (when used) be part of the tone rather than a replacement for tone.

entirely. I think many string players also overdo vibrato, often detracting from an authentic, convincing performance.
I think my vibrato (such as it is) is developing naturally, because although I haven't really been taught it, if we are working (for example) on tone or scales my teacher occasionally says "no vibrato for this". Well-placed, tasteful vibrato sounds good, but I agree that it is no disguise / replacement for a faulty tone.
....And so back to the practice!