Well, here's a good run-down from tax policy expert David Cay Johnston:
Congress requires the IRS to review every application for tax-exempt status to weed out organizations that are partisan, political, or that generate private gain. Congress has imposed this requirement on the IRS, and its predecessor agencies, since 1913.
So, it is likely that something that shouldn't have happened, did. But we shouldn't lose sight of the fact that the IRS shouldn't be giving blanket approvals for tax filing status (and, perhaps more importantly, for purposes of hiding donations and donors).
There's quite a few other important points made in Johnston's article. Check it out, and wish that most of those breathlessly talking about Watergate-level scandal had done so (because they obviously haven't).