I thought perhaps titletoc would permit this, but I see nothing about footnotes in the docs for that package.

Edit: I am using document class scrbook (needed for \multiplefootmarker, since the author's notes use numbers, while the editor's notes use * and other symbols). It is the editor who needs to annotate the Contents title.

-
What document class are you using? – egreg Dec 28 '12 at 20:33

# 1. book class

### Method 1 — Define a new command

The \ftableofcontents command wants as argument the text of the footnote.

\documentclass{book}
\usepackage{xpatch}

\expandafter\ftableofcontents\expandafter{\tableofcontents}
\xpatchcmd\ftableofcontents
{\contentsname}
{\contentsname\footnote{#1}\fi}{}{}
% Omit the following lines if you want the footnote with an arabic number
\xpretocmd\ftableofcontents{\begingroup\renewcommand\thefootnote{\fnsymbol{footnote}}}{}{}
\xapptocmd\ftableofcontents{\endgroup}{}{}

\begin{document}
\frontmatter
\ftableofcontents{This is the footnote}

\mainmatter
\chapter{A chapter}
\section{A section}
Here is a footnote\footnote{A}
\end{document}


### Method 2 — Overload \tableofcontents

In this case we redefine \tableofcontents to accept as optional argument the text of the footnote; nothing happens if no optional argument is specified.

\documentclass{book}
\usepackage{xpatch}

\expandafter\temp\expandafter{\tableofcontents}
\xpatchcmd\tableofcontents
{\contentsname}
{\contentsname\if\relax\detokenize{#1}\relax\else\footnote{#1}\fi}{}{}
% Omit the following lines if you want the footnote with an arabic number
\xpretocmd\tableofcontents{\begingroup\renewcommand\thefootnote{\fnsymbol{footnote}}}{}{}
\xapptocmd\tableofcontents{\endgroup}{}{}

\begin{document}
\frontmatter
\tableofcontents[This is the footnote]

\mainmatter
\chapter{A chapter}
\section{A section}
Here is a footnote\footnote{A}
\end{document}


# 2. scrbook class

The previous methods don't work with the scrbook class and it would be very difficult to patch the commands that produce the table of contents, so a hack seems the best thing to try (apart avoiding putting a footnote to a chapter title to begin with).

\documentclass{scrbook}

\begin{document}

\frontmatter

\begingroup
\makeatletter
\protected@edef\contentsname{\contentsname\unexpanded{\footnote{%
%%%% ADD HERE THE FOOTNOTE TEXT
This is a footnote%
%%%% DON'T FORGET THE FINAL %
}}%
\gdef\noexpand\contentsname{\contentsname}}

% Omit the following line if you want a number
\renewcommand\thefootnote{\fnsymbol{footnote}}

\tableofcontents
\endgroup

\mainmatter


# 3. Alternative method (all classes)

\documentclass{scrbook}

\begin{document}
\frontmatter

\itshape\footnotesize
\par\bigskip
}}}}

\tableofcontents

\mainmatter
\chapter{A chapter}
\section{A section}

\end{document}


-

You could try something like this (updated (thrice) to take into account egreg remarks)

\documentclass{article}

\begin{document}

\let\oldcontentsname\contentsname
\let\myif\iftrue
\def\myfootnotemark{\global\let\myif\iffalse\footnotemark}

\renewcommand\contentsname{\oldcontentsname\myif\myfootnotemark\fi}

\tableofcontents

\section{First}

\subsection{A}

\subsection{B}

\section{Two}

\subsection{C}

\section{First}

\subsection{A}

\subsection{B}

\section{Two}

\subsection{C}

\section{First}

\subsection{A}

\subsection{B}

\section{Two}

\subsection{C}

\section{First}

\subsection{A}

\subsection{B}

\section{Two}

\subsection{C}

\section{First}

\subsection{A}

\subsection{B}

\section{Two}

\subsection{C}

\section{First}

\subsection{A}

\subsection{B}

\section{Two}

\subsection{C}

\section{First}

\subsection{A}

\subsection{B}

\section{Two}

\subsection{C}

\end{document}


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If the TOC has more than one page ... – egreg Dec 28 '12 at 21:25
@egreg thanks for making me address this possibility. See the updated answer. – jfbu Dec 28 '12 at 21:31
The footnote mark will be added also to the headers. – egreg Dec 28 '12 at 21:35
@egreg see updated updated answer. – jfbu Dec 28 '12 at 21:48
it could be that in the code above \global\let\myif\iffalse would be better than \let\myif\iffalse, but as TeX is an experimental science for me and as it worked in my test file, I am leaving things like this ... until someone points out some flaw arising in more complicated situations. – jfbu Dec 28 '12 at 21:59