We find it interesting and somewhat courageous for Sen. Max Baucus, D-Mont., to join with his Republican Senate Finance Committee counterpart, Sen. Charles Grassley of Iowa, in order to put teeth into an investigation of lavish spending and lax oversight at a half dozen "prosperity gospel" ministries.

Their questions concern lavish spending for private planes and ocean-side mansions and involvement in for-profit businesses by such ministries and whether federal tax-exempt policies are effective.

Some of the ministries have not responded to questions the committee directed to them last fall, and the involvement by Baucus, the committee chairman, signals that subpoenas can potentially be used to compel responses.

Getting tough regarding such ministries' finances always raises concerns about government interference with religion, and makes other religious nonprofits wonder about the potential for stricter regulation on all such activities. And politicians are never eager to rile up their large and ardent flocks. But the committee certainly has a legitimate interest in seeing whether tax laws are working -- and whether this type of ministry is overly profiting from the donations of the vulnerable.

The United States, one of the most religious among industrialized nations, has a long history of all sorts of ministries, from tent revivalists to televangelists, and unfortunately, over the years some have been as interested in milking the gullible as in saving souls. That kind of abuse isn't likely to disappear, but as Grassley said, oversight is necessary to ensure that all taxpayers are getting a fair deal.