Many states have existing reciprocity agreements with their neighboring states, allowing workers, particularly those who live close to the state borders, to work in one state but pay income taxes in their state of residence. In recent years, however, as states are looking under rocks for more revenue, some of these reciprocity rules have been rescinded. But that's a different story. The Mobile Workforce State Tax Simplification Act of 2011 (we expect the year will change to 2012 if this ever becomes law) addresses the issue of workers who do a part-time gig in a state where they don't live.
Rather than have to file a tax return in each state where a worker logs some time, this legislation will allow employees to work in a state where they don't live for up to 30 days without owing income taxes to the state. The employee is not off the hook - he still must pay income tax on the income, but the tax liability would reside where the employee resides. However, athletes, entertainers, and politicians are not eligible to play by these rules. They are perceived to be earning enough money that the host states still want their cut.