http://www.debunking911.com/questions.htm
I googled "star wars death star exhaust port why". Now, why would I google that? Because we were talking about poor project management at work.
Hahaha!
My theory is the roofers who were contracted on the first Death Star figured that hey, there's not gonna be much work after this thing is done and paid off the structural engineers to build faults right into the substructure, the whole thing was ready to blow I tell ya!
Then they got a second lucrative contract but this time it was blown up by angry Bothans who'd had enough postal related deaths.