pgf(plots) node shadow/opaque pin

Is it possible to place a shadow/fill/opaque setting on text of a node pin? I know I can do that with the actual node, but I am using \node in pgfplots to mark some stuff on graphs, and it would be great if I could make a white filling in the text area to make it more clear. Of course, if you know a better way to achieve the same thing in pgf, let me know.

Code I've got so far is below. I tried putting something like [opaque=0.5] after pin, but it seems it has no such options, and I wasn't able to find anything relevant to pin text in pgf documentation.

\tikzset{small dot/.style={fill=black,
circle,scale=0.2}}

\node[small dot, pin=120:{$100\ k\Omega$}] at (axis description cs:0.5,0.61) {};

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Did you try opacity=0.5? –  Peter Grill Jan 11 '12 at 0:08

To get a semi-transparent background for your pin (or any other node, for that matter), you first need to specify some fill colour. So to get a semi-opaque node background, you could set fill=white, fill opacity=0.5, text opacity=1. Note that the text opacity needs to be set separately, since fill opacity applies both to the background colour and the text.

\documentclass{article}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
xmin=0,xmax=1,ymin=0,ymax=1,
grid=both, minor tick num=3, grid style=gray % Darker grid than normal to show the effect better
]
\node[pin={[fill=white, fill opacity=0.5, text opacity=1]120:$100\ k\Omega$}] at (axis description cs:0.5,0.6) {};
\end{axis}
\end{tikzpicture}
\end{document}

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I have been using \tikzset{every pin/.style={draw=black,fill=yellow!10}} which yields:

Code:

\documentclass{standalone}
\usepackage{pgfplots}

\tikzset{small dot/.style={fill=black, circle,scale=0.2}}
\tikzset{every pin/.style={draw=black,fill=yellow!10}}

\begin{document}
\begin{tikzpicture}
\begin{axis}[xmin=0,xmax=1,ymin=0,ymax=1]
\node[small dot, pin=120:{$100\ k\omega$}] at (axis description cs:0.5,0.61) {};
\end{axis}
\end{tikzpicture}
\end{document}

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This is a really great idea. –  henry Jun 7 '14 at 11:48