Baseball reminds exempt organizations that freedom isn't free

After three years of investigations, threats of more investigations and still ongoing perjury inquiries, the Congressional investigation of the Major League steroid scandal appears to have entered a hiatus.  But it's helpful to remember why Congress held such sway over the league's internal matters in the first place:  the implicit threat of revoking MLB's antitrust exemption.

A similar dynamic is in play arising from tax-exempt status for charities and other nonprofit groups.  Exemption gives Congress far greater power & incentive to intervene than it would otherwise have were these groups paying taxes. 

Will exemption always be worthwhile?