How many are being laundered is speculative.
I also think its safe to say that if we have large amounts of funds coming from mtgox accounts which no one has been able to withdraw from in months, these are stolen bitcoins. In my opinion these investments should be disqualified unless the "investors" are willing to come forward and make a statement regarding the legitimacy of these bitcoins. If they were purchased (somehow) then they should have no trouble backing that up.
If we have 100% sure that stolen Mtgox coins are used in this IPO, the MaidSafe admin can suspend the safecoin emission for these address until they proof the true or the identity.