I know of a few 'famous' individuals who have copious number of
articles appearing in top journals/conferences every year without
fail. Looking at their CV, it seems that they have a 100% success rate
at these top venues.
...
Or is it the case that there is a 'back door' or the individual or
institution reputation is so bright that any reviewers are obligated
to accept the article?
Those 'famous' individuals have submissions being rejected much much more often than you think.
I know this because my boss and my collaborators are also kind-of famous, ACM Distinguished Scientist, more than 100 papers etc etc, one even has more than 20k citations.
What is their strategy?
AFAIK, there is no such backdoor or reputation that can help you to get papers accepted, at least in my community. The strategy is to submit a lot of papers :) Last year, many people really got mad because ICSE, top conference in Software Engineering, only allowed 1 author to submit maximum 3 papers.
Think about it, while you think they are awesome because they have published a paper at ICSE, but behind the scene they got 4 or 5 papers rejected at the same time :)
Famous people often attract a lot of people who want to collaborate with them. They are often very successful in obtain funding, and have a big group to do research for them.
UPDATE
Answers to comments of Prof. Santa Claus.
What do they do with those rejected papers? Revise and submit next
year? or do they dump them into lower ranked conferences? Is the
strategy then to always push all rejected papers, given 'infinite
time', into top venues?
Of course revise and re-submit, but why wait until next year? If your paper is rejected at ICSE, the next step should be to re-submit it to either one of ECOOP, ISTTA, FSE, ASE, ICST...(the list doesn't end here) which are in the same rank, or just a bit less. Famous people, with their vast experience, do not submit paper which doesn't stand a chance. After being rejected, they know where the problem is, and know how to improve the paper to be accepted.
a 'back door' is simply to send a draft of your paper to likely
reviewers for the conference. If you are famous, you tend to know most
of the people on the program committee anyway -- birds of feather
flock together. You get their feedback and if they hate it, don't
submit. If they like it submit.
There are more than 20 PC members, who you should send your paper to? To the ones who work in the same problem? But they are direct competitors :) And you do this every time you want to submit a paper,i.e. 10-15 times per year, you will piss them off. If you think your paper is good, submit it regardless of what other people/reviewer think.
By the way, all the conferences I mentioned adopt double-blinded review. And you need to mark conflict PC members, who are your advisor/advisee, collaborators, institutional colleagues and so on. What you just said doesn't seem practical in the communities I know.
Another backdoor is that you know the EiC of a journal and you can
give him/her a call when there is a reject. I know of a prof who does
this regularly. Also, look up 'guanxi'. If you have enough of this,
papers get in, and this is the 'normal' practice of certain people.
Is this "quanxi" only a Chinese thing? I don't think you can do this for top journals/conferences.
What is the success rate of your boss(es) at top venues
If "success" means eventually (even after some rejections) appear in top venues, then it would be more than 90% :) If you include also the rejections, then 60% is a rough guess.