A CPA got disbarred for not doing due diligence on information provided to him by his clients. The situation dealt with a corporation and the husband and wife shareholders. The appellate Authority observed that, "it was inconceivable that [the individual taxpayers] could pay their living expenses based in the income reported on their returns."
The CPA did not show up for his administrative proceeding and was disbarred. He then appealed the disbarment and lost.
Read up on your Circular 230. The IRS press release is here