According to this CnnMoney.com article: http://money.cnn.com/2011/03/09/news/economy/irs_budget
The IRS collects between $3-$4 for every dollar it spends, and according to the Obama Administration the IRS should be expanded to further enforce the tax code and help shrink the deficit.
I think this is a big mistake. A lot of the proposed hiring of new IRS Agents is 100% linked to Obamacare and enforcing the tax and reporting provisions contained in the law. Since the law is almost guaranteed to be declared unconstitutional by the Supreme Court this is just an end-run to get more government employees on the books before the law is thrown-out.
We all know what happens once government employees are hired: they stay around until they retire or quit - regardless of if they are actually needed or they are actually performing a valuable function.
Rather than further increase the heavy hand of the government, why not revise and simplify the tax code so that all these IRS agents are not needed? There is no reason to have a tax code that 90% of Americans are unable to interpret on their own without the help of a tax lawyer or accountant.