One company I am familiar with is a private company that will never go public. They give stock to their employees, and in fact, 100% of their stock is owned by employees (down from 49.9999%, when 50.0001% was owned by the founder). They have zero outside investors. The value of the stock is set by some sort of auditing firm, but there's no actual market valuation.

If this doesn't sound questionable enough, keep in mind that this is the only retirement plan they offer to employees and that upon leaving the company employees are required to sell back their shares.

Maybe it's totally legit, but it always struck me as very, very questionable.