This might also involve the questions: What is the appropriate length of a Code Review question? and Should line numbers for code snippets be added?
Since this is code review, I imagine the length of many questions could be immense. Just as an example: my recent one on a custom mysqli/spl class dumped on pastebin, where each part of the entire code could affect the accuracy of an answer. Encouraging posting code here is good. Encouraging posting only relevant snippets to the question is good. But what a poster may be trying to convey could be distorted by throwing an entire code dump in a question or trying to trim off excess lines just to make things neater? There could be something in those trimmed lines that would change an answer.
What if stackexchange hosted their own paste bin or a side-module where the user can dump code related to the question? For example: two tabs showing on a question page: default tab #1 shows the full post, answers, comments as normal; tab #2 shows the code complete with syntax highlighting, comments by line#, etc. This way, content is still maintained within SE, entire code dumps are possible for a question, and length of posts get shorter?