There's a big problem with Kennedy Space Center playing host to the Constellation Program: The heavy-lift rocket, Ares V, may be too heavy for the infrastructure to cope with. The crawlerway is a 40 year old road designed for the Saturn V (Apollo Program) crawler-transporters and is currently used to carry the Shuttle up to 6.8km (4.2 miles) from assembly building to launch pad. The crawlerway may be unable to withstand the weight of the fully-laden Ares V, transporter and mobile launch pad; a combined weight 33% heavier than anything the Kennedy crawlerway has ever supported.
I saw a hysterical comment about this matter on some site. It read:
When I first came here, this was all swamp. Everyone said I was daft to build a 10.9 million kilogram rocket on a swamp, but I built it all the same, just to show them. It sank into the swamp. So I built a second one. That sank into the swamp. So I built a third. That burned down, fell over, then sank into the swamp. But the fourth one stayed up. And that's what you're going to get, lad, the strongest rocketship in all the world.