I don't have any links for this, but it seems to me that Democrats and Republicans often get a pass when they violate some minor campaign finance rules. These same seemingly insignificant rules are then used to bludgeon to death an unsuspecting grass-roots campaign.

When it comes to ballot access, the rules are often waived or forgiven for Democrats and Republicans. In the name of "democracy" you just have to have the Big 2 on the ballot. Wasn't that the argument of the NJ Supreme Court when Torricelli dropped out of the Senate race in 2002? The Democrats dusted off Lautenberg and entered him in the race after the deadline. The argument of the NJSC wasn't that the law as written was ambiguous. The law was actually very clear. Their argument was that people must have a "real" choice. In the collective mind of the NJSC, the four other independent candidates running didn't count as "real" choices even though they had jumped through more hoops than the Big 2 candidates in order to get on the ballot. I doubt the NJSC would have granted the same privilege to any serious third-party contender.

Many of the comments imply that this is done intentionally to exclude outsiders, or alternatively, it is simple "unintended consequences".

I want to propose an explanation for how these laws can systematically produce this sort of bias without any intent to harm/exclude others. The basic idea is that the people who write these laws are limited by their own experiences -- they try to make the laws reasonable, but they only know what is reasonable for someone in a situation similar to their own. The authors tend to be bureaucrats (either governmental or corporate) and just take for granted the idea that everyone in the country has the resources and mentality that allows them to read massive rule books, keep detailed records, and submit paperwork on time. 

By assuming that the world works in a particular way, they build rules around those assumptions, inadvertently prohibit other ways of living. This is similar to the price-calculation problem, in that no matter how well intentioned a governor is, he can't understand the totality of the society that he governs.