This doesn't come as a big surprise:
The tax-writing Ways and Means Committee is planning a hearing to look into the “organizational structure, management, and financial growth” of AARP. [...]
“AARP is known for being the largest and most well known seniors' organization in the country,” Herger said in a statement. “But what Americans don't know is that AARP was the 4th highest spending lobbying organization between 1998 and 2010 or that the AARP brand dominates the private Medicare insurance market. This hearing is about getting to the bottom of how AARP's financial interests affect their self-stated mission of enhancing senior's quality of life. It is important to better understand how AARP's insurance business overlaps with its advocacy efforts and whether such overlap is appropriate.”
Basically, House Republicans are investigating the AARP in retaliation for this:
“AARP is proud to endorse the Affordable Healthcare for America Act. We urge members of the House to pass this critical bill this year so our healthcare system can work for all of us,” AARP CEO A. Barry Rand said at a press conference.
If you remember, conservatives were outraged by the AARP's endorsement of health-care reform. Indeed, the following year, the "Alliance for Retirement Prosperity" was launched the following year as a conservative alternative to the organization. In other words, this upcoming hearing has less to do with the AARP's 'organizational structure, management, and financial growth" and more to do with the fact that it supported a policy Republicans don't like.