This story, on David Garrow's criticism of Justice Blackmun for relying too heavily on his clerks, is quite typical in quoting adoring former clerks who strongly defend Blackmun. Have you ever seen a story about a Justice where the clerks are portrayed as anything but adoring? Have all the Justices for the last fifty years really been so adorable? Just once, I'd like to see a former clerk quoted along the lines of, "yes, my Justice was slipping a lot there toward the end, and let us clerks do too much of the work. He could sometimes be an obnoxious jerk, often went into partisan tirades against the president, and was occasionally known for drinking too much and embarassing himself in front of young female clerks. But he tried his best, and he's only human, you know."
David raises an interesting question, though I wonder whether "obsequiousness" is quite the right term.
My sense is that clerks have tremendous loyalty to their former Justices. Generally speaking, this loyalty comes from a mixture of (1) genuine affection -- to my knowledge, virtually all the Justices who have sat in the last 15 or so years (and possibly even further back) have been very nice to their clerks -- (2) gratitude, and (3) a social norm among Supreme Court clerks, under which many will interpret criticism as disloyalty, ingratitude, or lack of affection. This is a very broad generalization, so I'm sure it has many exceptions; for instance, I suspect that there are some ex-clerks who don't subscribe to the norm mentioned in item 3, and don't enforce the norm. The generalization also generally does not extend to polite criticism of the Justice's opinion or jurisprudential philosophy. (Note also that the duty of confidentiality as to in-chambers conversations or happenings is a separate matter.)
This loyalty may be good, bad, or a mix of both. Loyalty generally has pluses and minuses, because it usually shows itself when the loyal behavior is different from the behavior that one would otherwise think is most correct -- most candid, most law-abiding, most respectful of the rights and interests of others.
If I fail to report my son's (purely hypothetical!) embezzlement, my loyalty to my son is keeping me from helping enforce the law, helping remedy the wrong, helping protect the victim of the embezzlement, and helping prevent and deter future bad conduct on my son's part. That's why some people would criticize such loyal behavior; and yet it seems to me that there is value to such loyalty, too (though I haven't thought hard about the theoretical framework for analyzing such matters, and in any event wouldn't have the time to elaborate on any such framework here). Likewise, former Supreme Court clerks' loyalty causes some problems -- it keeps discussions about the Justices from being as candid as they could be -- but may also have some merit.
But the bottom line, I think, is that such loyalty doesn't deserve the more or less unalloyed condemnation that the term "obsequiousness" suggests. Obsequiousness tends to refer to a desire to ingratiate oneself, and to win benefits through flattery. And while loyalty might involve a desire not to lose benefits (to the extent that perceived disloyalty may lead to social, personal, or professional punishment), there's more going on there than just this desire -- and some of what's going on ranks in the better portion of human nature rather than the worse.