http://www.fourwinds10.com/siterun_data/government/fraud/us_government/news.php?q=1237576392
http://www.govtrack.us/congress/billtext.xpd?bill=h111-1388
http://www.americorps.gov/about/newsroom/releases_detail.asp?tbl_pr_id=1265

Under section 6104 of the bill, entitled “Duties,” in subsection B6, the legislation states that a commission will be set up to investigate, “Whether a workable, fair, and reasonable mandatory service requirement for all able young people could be developed, and how such a requirement could be implemented in a manner that would strengthen the social fabric of the Nation and overcome civic challenges by bringing together people from diverse economic, ethnic, and educational backgrounds.”
Section 120 of the bill also discusses the “Youth Engagement Zone Program” and states that “service learning” will be “a mandatory part of the curriculum in all of the secondary schools served by the local educational agency.”
Obama told a rally in Colorado Springs, “We cannot continue to rely on our military in order to achieve the national security objectives we’ve set. We’ve got to have a civilian national security force that is just as powerful, just as strong, just as well funded.”

Despite denials that Obama plans to institute a mandatory program of national service, his original change.gov website stated that Americans would be “required” to complete “50 hours of community service in middle school and high school and 100 hours of community service in college every year”. The text was only later changed to state that Americans would be “encouraged” to undertake such programs.
If you believe it will be voluntary you need to see what the government said about income tax and social security when it passed those pieces of legislation.