I found a good article about how Standards & Poors decides which companies are included in the S&P 500 index. It's from quite a while ago (year 2000), but it's somewhat definitive as it was written by David Blitzer himself. See ETF.com - Here, At The S&P 500 (archive copy).
While the article focuses on the criteria for company inclusion in the indices, there are some mentions of the Index Committee, w.r.t. why it exists and how it is made up.
Here are some notable excerpts from that article specifically about how the Committee operates:
[...] Standard & Poor's does not use an index committee to avoid rules
and guidelines. In fact, the Committee not only uses guidelines but
also publishes the guidelines (see box nearby) and explains how they
are applied to specific index actions. Standard & Poor's uses a
committee because we feel it is not possible to develop rules that
will deal with any and all market events. [...]
... and an interesting anecdote about the Committee's decision on adding AOL to the index; all emphasis below is mine:
[...] During much of 1998 the stock's possible entry into the S&P
500 was a matter of wide speculation. Not wanting to encourage the
speculation, Standard & Poor's watched the discussions from the
sidelines. We do not want to move markets with our decisions if that
is avoidable. That is not one of our goals as an index provider; in
fact, one of our goals is to avoid unsettling markets. [...]
By late in the year, the discussions began to fade as many market
commentators decided that Standard & Poor's would never add AOLto [sic]
the S&P500. With the hype fading, Standard & Poor's announced the stock's
addition to the index as a replacement for Venator (formerly
... a part of the article specific to the makeup of the Committee itself:
[...] The Standard & Poor's Index Committee has nine members, all Standard &
Poor's employees. All members are drawn from the Investment Services
group at Standard & Poor's and all have various job responsibilities
related to the indexes and the equity markets. The Committee includes
two analysts monitoring the companies in the index who provide
necessary support and index-management expertise within the Committee. [...]
Some investors and journalists seem to have images of pitched debates
over issues that will move the stock market. As disappointing as the
truth might seem, this is rarely, if ever, the case in the Index
Committee. Most decisions have very limited, if any, market impact.
Relatively few issues are hotly debated. The process is based on
developing a consensus, not scoring debating points. Discussions where
there is initial disagreement will continue until everyone has had an
opportunity to present his or her view and a consensus has emerged.
While most of the issues mentioned in this article were discussed in
the Committee, none were the subject of any pitched debates. Moreover,
we make sure that none of the Committee members disagrees with the
ultimate decisions. [...]
... a section about confidentiality, where the Committee is mentioned:
Changes in the S&P 500 and other Standard & Poor's indexes do
sometimes move stock prices. Because of this, Standard & Poor's
considers all index changes and announcements to be market sensitive. [...]
All members of the Index Committee plus other Standard & Poor's staff
who work on index matters and have access to index information are
subject to certain restrictions on their personal securities
investments and trades.
... and a section on transparency, where the Committee is also mentioned:
We do not, however, encourage extended conversations [with the Index Committee]
with those who want to know what they have to do to get a company into the S&P 500.
Overall, in the article Blitzer does not specifically mention confidentiality with respect to the individual membership of the Index Committee, but I think it's reasonable to assume that Committee membership is not published in order to reduce the possibility of outside influence on its members.
Here's another related article, also by David Blitzer: Indexology Blog - Inside the S&P 500: An Active Committee (archive copy).