Forces you to focus on legibility.
Emphasis on short.
Encourages preserving source control blame
Long lines raises concerns on naming
Some languages may not be suitable for 80 characters.
Can make some functions or conditions longer
When writing conditions, consider breaking them into multiple conditions. See below for reasoning.
The focus on short may may become bad.
Example: Bad variable names.
Example: Too many small functions. Makes it difficult to understand flow.
Aim for balance.
Not everyone has the same screen size as you
Choose the lowest common denominator
URLs. Always try to use full URLs as much as possible as it helps the reader to intuit the purpose of the URL.