In Australia it is common for voters to receive letters from their political representatives, and these letters are becoming more and more sophisticated in targeting the interests of the individual voters.

The two major political parties are able to do this because they have established databases. The inner workings of the databases have been somewhat elusive, but Wayne Errington and Peter van Onselen have written an academic paper (warning- PDF file) on how these databases work. The implications for the privacy of voters are odious, especially considering the temptations for political parties in government to cross check their party databases with government ones.

I found this via Ken Parish, and check out the comments on his post where Wayne Errington makes some further good points about the database's operation. He says the saving grace (so far) is that the political parties are actually rather slack in maintaining their databases; however, as time goes on, you can expect the party machines to become more professional in this matter.