The massive bombing casualties in Baghdad and Karbala are a clear sign that there will be no end to muslim deaths in Iraq until Al Queda's infrastructure is destroyed and sufficient well trained and experienced local forces are available to both secure against attacks and take away any excuses that some might still have that Al Queda is an anti-occupation force.
Such a large operation could not have been done without a support structure in place locally. But if the inter-confessional war that Al Queda clearly wants to break out actually happens, that infrastructure is likely to grow, destabilizing Iraq and raising the possibility of a regional war.
In the end, the solution will be a general muslim determination that muslims killing other muslims to provoke further war against muslims earns the perpetrators a place in hell. A useful exercise that outsiders can further is to encourage all imams to pronounce on the issue and to advertise those who are pro-fratricide and who support them.