The response to that concern at the time was that most of the people who would know how to get around it wouldn't need to sockpuppet[1]. I suspect, if it were ever implemented, there'd be some attempt to obfuscate or hide what was actually tracked like they do for their other fraud algorithms. But issues like that and the privacy issues were pretty indicative of its lack of value and it doesn't surprise me it was never implemented and didn't even warrant a response from an SE employee.
[1]: http://meta.stackoverflow.com/questions/113394/implement-som...