What are common pitfalls Software/System/Web Developers and Engineers face regarding collaboration? How can they be avoided or mitigated?

This is a point towards inter-team collaboration, and I hope I understood the question right.

One thing I have noticed is style. Some people choose "shortcuts" while others don't. This is especially true when using untyped languages like Python.

Take for instance this:
x = True
print "Hello" if x else "World" is the same as:

if (x):
....print "Hello"
else:
....print "World"

This is a simple example and there are many more "shortcuts" and style related things out there and I understand the need or want for them.

As much as I am personally against this, I believe it could be beneficial for organizations to implement a style guide, even informally. Seasoned developers are able to decipher these, but new members or other people inheriting code without a full understanding can run in to problems discerning the functionality of certain pieces of code.

*Edit: it got rid of my indentations, so I made them periods (.).

Clearly described, defined requirements with a user group that has a specific functions and automated testing scripts for scalability across many geographic regions.
Coding for millions of users with billions of transactions requires efficient code.
This software must be put through real world production scale environments.