The NY Times has an article this morning, Federal Budget Crisis Months in the Planning, by Sheryl Stolberg and Mike McIntire, describing how conservative groups planned months in advance to use the continuing resolution and the threat of a government shutdown to try to defeat Obamacare. According to the article, "[t]he billionaire Koch brothers, Charles and David, have been deeply involved with financing the overall effort. A group linked to the Kochs, Freedom Partners Chamber of Commerce, disbursed more than $200 million last year to nonprofit organizations involved in the fight."
The Times has a link to a FreedomWorks "Coalition Letter" by Matt Kibbee, dated February 14, 2013, activists that explains why they are opposed to Obamacare:
On October 1, 2013, open enrollment begins for the federally backed health care exchanges. On January 1, 2014, new money from Washington will begin flowing to states and individuals, all but ensuring that these new entitlements will become a permanent fixture of life in America. The window of opportunity to stop the implementation of these massive new subsidies is closing. Although many of Obamacare's provisions are now the law of the land, many of the law's most damaging and irreversible provisions do not take effect until 2014.
Once implemented, the new spending contained within Obamacare, primarily the Medicaid expansion and exchange subsidies, will cost taxpayers more than $1.6 trillion over the next decade, according to the latest CBO estimates. Given the history of federal entitlement programs and the back-loaded nature of Obamacare spending, some estimate the full implementation cost could reach $2.6 trillion over ten years. It will increase the federal government's health spending by 15 percent.