Not only did the sunnis boycott the elections, but there were countless situations where certain towns did not receive their ballots, other towns got their polling stations closed before voting started, etc etc. These elections were rampant with irregularities. That´s why it was a sham.
And then there´s a simple fact that most people fail to pay enough atention to: Because of the boycott, the new govt is not a representation of all iraqi minorities. Lots of people will feel left out, wich will cause a lot of friction between them. With the current security chaos, and the fact that sunnis and shiites are at eachother´s throat everytime they can, these results are liable to throw another proverbial logg in the fire. Civil war is a definitelly possibility. Some would say that not only it´s a possibility, it´s already happening. Mosques are getting blown in a weekly basis, assassinations, vendettas, etc etc. A real cauldron of hatread.