Geht nicht und ist genau so dokumentiert.
![alt text][1]
Man kann natürlich den Beamer `frame` hacken, dann sind aber alle Fußnoten auf der ersten Folie.
\documentclass{beamer}
\makeatletter
\def\beamer@autobreakframebox{%
\global\setbox\beamer@splitbox=\box\voidb@x%
\ifbeamer@autobreak%
% Ok, frame was overful -> split it!
\setbox\@tempboxa=\vsplit\beamer@framebox to\beamer@autobreakfactor\textheight%
\global\setbox\beamer@splitbox=\box\beamer@framebox%
\@tempdima=\ht\beamer@splitbox%
\ifdim\@tempdima<\beamer@autobreaklastheight%
\global\beamer@autobreaklastheight=\@tempdima\relax%
\else%
\setbox\@tempboxa=\vbox{\unvbox\@tempboxa\unvbox\beamer@splitbox}%
\global\setbox\beamer@splitbox=\box\voidb@x%
\fi%
\setbox\beamer@framebox=\vbox to\textheight{\unvbox\@tempboxa%
\vskip\beamer@framebottomskipautobreak%
%\ifvoid\beamer@splitbox% <-- Commented
\ifvoid\beamer@footins%
\else%
\begingroup
\usebeamercolor*[fg]{footnote}%
\footnoterule%
\unvbox \beamer@footins%
\global\setbox\beamer@footins=\box\voidb@x%
\endgroup
\fi%
%\fi% <-- Commented
\beamer@exitcode%
}%
\else%
\setbox\beamer@framebox=\vbox to\textheight{\unvbox\beamer@framebox%
\vskip\beamer@framebottomskip%
\ifvoid\beamer@footins%
\else%
\begingroup
\usebeamercolor*[fg]{footnote}%
\footnoterule%
\unvbox \beamer@footins%
\global\setbox\beamer@footins=\box\voidb@x%
\endgroup
\fi%
\beamer@exitcode}%
\global\setbox\beamer@footins=\box\voidb@x%
\fi%
}
\makeatother
\begin{document}
\begin{frame}[allowframebreaks]
\begin{itemize}
\item Item\footnote[frame]{First frame footnote}
\end{itemize}
\input knuth
\input knuth
\begin{itemize}
\item Item\footnote[frame]{Second frame footnote}
\end{itemize}
\end{frame}
\end{document}
![alt text][2]
[1]: http://texwelt.de/wissen/upfiles/test_325.pnghttp://texwelt.de/wissen/upfiles/test_325.png
[2]: http://texwelt.de/wissen/upfiles/test_326.png
