I wonder if someone can let me know the top 10 most active researchers
on Google Answers, based on the number of questions asked, and subject
to (i) each such person receiving at least a 4 and 1/2 (or fraction)
or 5 star ranking, and (ii) advising how many refunds each person was
obliged to make?

Google Answers Researchers do not have access to detailed statistics;
we can only search the site, just as other users do. I have compiled a
list of the ten most active Researchers that I believe to be accurate.
If I've made an error, I hope one of my colleagues will post a
correction.

bobbie7-ga
Average Answer Rating: 4.78 stars
Questions Answered: 1780
Number of Refunds: 4

juggler-ga
Average Answer Rating: 4.76 stars
Questions Answered: 1564 
Number of Refunds: 5 

pinkfreud-ga
Average Answer Rating: 4.88 stars
Questions Answered: 1258
Number of Refunds: 6

tutuzdad-ga
Average Answer Rating: 4.62 stars 
Questions Answered: 929 
Number of Refunds: 5 

scriptor-ga
Average Answer Rating: 4.76 stars
Questions Answered: 918 
Number of Refunds: 7 

easterangel-ga
Average Answer Rating: 4.47 stars  
Questions Answered: 895 
Number of Refunds: 5 

justaskscott-ga 
Average Answer Rating: 4.56 
Questions Answered: 777 
Number of Refunds: 4 

politicalguru-ga 
Average Answer Rating: 4.50 
Questions Answered: 694 
Number of Refunds: 5 

pafalafa-ga 
Average Answer Rating: 4.63 
Questions Answered: 607 
Number of Refunds: 8 

missy-ga 
Average Answer Rating: 4.61 
Questions Answered: 581 
Number of Refunds: 7 

I hope this is precisely what you need. If it is not, or if anything
is unclear, please request clarification; I'll gladly offer further
assistance before you rate my answer.

Best regards,
pinkfreud

Yes, that was precisely what I was looking for, pinkfreud.  Many
thanks.  And the additional comments so kindly provided by summer95,
larre, probonopublico and pafalafa very nicely round out the
information.  Much appreciated, all!

As a slightly related aside, probonopublico is not an official Google
Answers researcher, but he/she comments quite often and has ask quite
a few questions. A search for "probonopublico" shows 1927 hits. I
certainly didn't look at all of them, but I'm sure that probonopublico
either ask or commented on most of those.

Researchers with the highest quality ratings and fewest, or no refunds
are often "active" but not necessarily the most prolific.

bethc 4.89
http://answers.google.com/answers/ratings?user=5382948337570492913
inquisitive 4.84
http://answers.google.com/answers/ratings?user=6480027774368830747
googlenut 4.83
http://answers.google.com/answers/ratings?user=5706088326173856389
leli 4.82
http://answers.google.com/answers/ratings?user=4216402838464863991
mathtalk 4.84
http://answers.google.com/answers/ratings?user=7140600057608697771
markj 4.88
http://answers.google.com/answers/ratings?user=8249429130518388147

By no means a comprehensive list, just those I'm aware of off the top
of my head. ---l

Wow, Summer 95 ...

I knew I was verbose but I had never quantified it!

Of course, I have never answered any Question, as such, I just chip in
on someone else's question that I find particularly interesting.

I would never dare to become an Official Researcher because I am sure
that I would soon set a record for the worst Star rating ever.

Incidentally, from my experience, I am delighted to confirm that all
the Researchers do first class work BUT ...

I don't think that they always get the Stars that they deserve.

Too often, I have seen Questioners who have been DELIGHTED with their
Answers and yet they have still given less than 5 Stars.

C'est la Vie!

All the Best

Bryan

Special mention must be made of the work of boquinha-ga, who has --
astoundingly -- maintained a perfect 5.0 rating through the first 54
questions this researcher has answered.

Thank you very much for the five-star rating and the generous tip!

~pinkfreud

Why, thank you, Pafalafa-ga! I've been rather busy and haven't
answered a question in a while, but I do pop in to Google Answers now
and then. What a treat to see your kind comment!

Sincerely,
Boquinha-ga

You have forgotten Robertskelton-ga:

Average Anser Rating: 4.64
Questions Answered: 654
Number of Refunds: 3

Also Justaskscott-ga:

Average Answer Rating: 4.56
Questions Answered: 777
Number of Refunds: 4

Bowler,

Justaskscott-ga was on my original list. I did omit Robertskelton-ga,
who has been less active lately. I apologize for the omission.