In case the link disappears behind a paywall, you can access it for free via Google: a nervy approach to retirement saving site:wsj.com - Google Search
, click on the first link.
I found a credible source, the SEC: Investor Alert: Self-Directed IRAs and the Risk of Fraud
A self-directed IRA is an IRA held by a trustee or custodian that permits investment in a broader set of assets than is permitted by most IRA custodians.
Most IRA custodians are banks and broker-dealers that limit the holdings in IRA accounts to firm-approved stocks, bonds, mutual funds and CDs. Custodians and trustees for self-directed IRAs, however, may allow investors to invest retirement funds in other types of assets such as real estate, promissory notes, tax lien certificates, and private placement securities.
While self-directed IRAs may offer investors access to an array of private investment opportunities that are not available through other IRA providers, investments in these kinds of assets may have unique risks that investors should consider. Those risks can include a lack of disclosure and liquidity -- as well as the risk of fraud.
Somewhat less credible is Wikipedia, but it contained the SEC reference: Self-Directed IRA
I also retitled your thread.
To some, the glass is half full. To others, the glass is half empty. To an engineer, it's twice the size it needs to be.