Pidgin stores you passwords in plain text in ~/.purple/accounts.xml.Someone can easily boot into recovery mode while you are away and find your passwords in plain text.
Download the patch from here into the same directory and do the following
tar xf master-password.patch.tar
patch -p 1 < master-password.patch
You should be ready to configure, make, and install as normal.
sudo make install
When you launch pidgin, you will see a new tab in the preferences called "security". You can set a master password there. The link above has screenshots. After configuring, you should notice that the accounts.xml file now has gibberish where there once were passwords.
To remove pidgin, run the following from the directory in which you built pidgin
This will work for pidgin 2.1.0,2.1.1 versions.