As for PytagoraZ participation on the contest, the edition that I am running doesn't state rules to deal with this kind of behaviour and I don't know if it would be fair to insert them right now considering the stage of it. I will consider this a lesson learned and, if the next edition happens by me, will surely take this into consideration in order to create a more fair contest amongst everyone.
Overall I tend to agree with GazetaBitcoin perspective (considering that the contest doesn't have a rule for this scenario but I am open to discussion):
But since this is a forum where free speech is encouraged as much as it is possible, this involves also that people can vote for him and his pie. Receiving votes may look abnormal or immoral but, since no contest rules are broken, I don't think there is anything which can be done.
Personally I would bar alt accounts from entering the contest -- I mean a lot of the ones that don't even look like pies are probably all made by the same person or people. But of course its not always easy to prove who is or isn't an alt, etc.
For the price prediction contests though, that's just pure scumbaggery to use multiple accounts in the same contest. I frankly don't care if its in the contest runner's rules or not, for me it implies an inherent trustworthiness.
There is one sizable farm that actually all enters these contests together. I busted about half of them, was just getting annoying seeing them all take advantage of other peoples' generosity and nobody noticing or doing anything about it... Will get around to them next.