I just read a great article by Paul Graham entitled Hackers and Painters. There were a lot of great quotes and ideas in it but here are two I liked most:

Everyone by now presumably knows about the danger of premature optimization. I think we should be just as worried about premature design-- deciding too early what a program should do.

When a piece of code is being hacked by three or four different people, no one of whom really owns it, it will end up being like a common-room. It will tend to feel bleak and abandoned, and accumulate cruft. The right way to collaborate, I think, is to divide projects into sharply defined modules, each with a definite owner, and with interfaces between them that are as carefully designed and, if possible, as articulated as programming languages.

His ideas about a loosely typed language allowing for increased changability made sense but I wonder if that wouldn't just increase problems at debugging time instead of compile time. Probably not if you had good tests.