Credit Mobilier: "The distribution of Crédit Mobilier stocks by Congressman Oakes Ames along with cash bribes to congressmen"
Teapot Dome: "control of U.S. Navy petroleum reserves at Teapot Dome in Wyoming and at Elk Hills and Buena Vista in California, were transferred from the U.S. Navy Department to the Department of the Interior"
And Army-McCarthy, Watergate and Iran-Contra are all obviously directly tied to the government.
In those cases it makes sense for Congress to get involved. It's when Congress start to investigate "private citizens whose activities suggest the needs for legislative remedy" that I get concerned. That type of broad power apparently gives them free-reign to investigate anything they don't like.
It seems to me that in the past (15 or 20+ years ago) Congress didn't get involved in non-government related "scandals" like Toyota and college football, I'd be interested if anyone has examples to the contrary.