There was a patch/hack released for the Beta, so I wouldn't be surprised if those clever gamers didn't find a way to do it with the release version as well...
As far as I know Miano, the hack was for the single player campaign only. Said hack allowed the user to play through the entire (not 100% sure) storyline, it did NOT allow for the use of LAN.
Recently a "pro" version was released by Blizz for use in tourneys that does allow the use LAN, however this "pro" version is only available for the duration of the competition. Additionally, a Blizz employee (to the best of my knowledge) physically watches over the version to prevent it from reaching the public. (Ten bucks its going to get torrented within 10 days of release)