Cornell Law Professor William Jacobson points out that in both the House and Senate versions of Obamacare, enforcement of the "individual mandate" requirement would be assigned to the tender mercies of the fine folks at the Internal Revenue Service.
These reporting provisions would allow the IRS to cross-check income tax returns and health coverage filings, and withhold tax refunds or utilize other collection methods for persons who do not have coverage unless they can prove they have acceptable coverage from some other source.
As usual with the IRS, you would be guilty until proven innocent to their satisfaction. Yeah, we just LOVE the idea of the IRS as our national health care enforcer. Professor Jacobson goes on in other posts to point out that under the Senate bill, the amount of the penalty tax would be left up to the discretion of the IRS, and that under both bills this amounts to a tax for merely existing.
As to combining your health information and taxation, those infamous Nazi racist un-American evil-mongering AstroTurfing far-right-wing-extremists at the American Civil Liberties Union have produced a brief Flash film on where letting the government have too much information can lead. Why, there seem to be no limits on the scare tactics this Republican front group is willing to use against Obamacare!
(I wonder if Orwell ever thought that Big Brother could turn out to be the Pizza Boy?)