There are, of course, many different opinions with regards to feedback...
Historically, many sellers liked to have it piled it on, preferably
into the thousands, as this demonstrates a level of both credibility
and trust... and rightly so...
Some seem to never get enough, and, indeed (do) chase their customers
for it, which, as some have mentioned above, can become risky business...
Some really need to learn when "enough is enough"... if you are able
to sell everything you list, and people are noticing your listings,
and you have repeat buyers, think about it... does it really matter?
And for those already up into a high number (relatively speaking)...
how much credibility do you feel you need?
We have had 31,700
ebay transactions, and have only received 18,200
feedbacks... this represents 57% ... and this has been in 9 years...
at this stage, it really doesn't matter to us whether we ever receive
another feedback... we've established ourselves and our reputation...
nothing else really matters...
Lastly... we quit giving buyers 'instant feedbacks' more than a few
years ago, and, now, only issue them when buyers message us for them.
Like I said... there's many schools of thought with regards to the
feedback system... the above is ours.