Argument: Earmarks are susceptible to bribery and corruption
David Heath and Hal Bernton. "$4.5 million for a boat that nobody wanted". Seattle Times. October 14, 2007 - Earmarks are federal dollars that members of Congress dole out to favor seekers — often campaign donors. In the process, lawmakers advocate for the companies, helping them bypass the normal system of evaluation and competition. This can result in earmarks that are wasteful or potentially harmful. [...] This can result in earmarks that are wasteful or potentially harmful.
[...] People who benefit from earmarks generally give money to those who deliver them: Of the nearly 500 companies identified as getting 2007 defense earmarks, 78 percent had employees or political action committees who made campaign contributions to Congress in the past six years.
Though individual contributions are limited by law, people at companies that received defense earmarks gave lawmakers more than $47 million.
The 2,700 earmarks Congress put in the 2007 military spending bill cost $11.8 billion. The Pentagon didn't ask for the money in its budget and, because its budget is capped by law, cuts had to be made to find room for the favors.
Lawrence Lesig. "the wrong in earmarks". Lesig Blog. September 11, 2008 - the problem with earmarks is that they've become an engine of corruption. The explosion after the Republicans took over under Newt was because they were a newly deployed source of influence, designed (too often) to induce or repay a gift (or what others call, a campaign contribution).
Jon Henke. "Why Earmarks are a Problem". March 13, 2008 - earmarks are the primary fulcrum for outside interests to corrupt the legislative process. Earmarks are the source of much of the undue power of individual Congressmen.