(Bloomberg Business) — To judge by Amazon's 401(k) plan, the giant online retailer doesn't have much in common with its more benevolent Silicon Valley peers. The workplace culture now under scrutiny for its reportedly brutal tendencies is paired with a comparatively stingy and risky retirement plan.

The match of employee contributions into their 401(k) plans is below average and made entirely in Amazon stock, which leaves employees dangerously exposed to the company's fortunes. In fact, Amazon's 401(k) came last in Bloomberg's ranking of the plans offered by the top 50 companies in the S&P 500.

The general trend in this group has been to move away from matching employee contributions with stock. Part of the reason stretches back to the collapse of Enron, when workers saw retirement savings, which were heavily invested in Enron stock, destroyed right alongside their employer. A survey by Aon Hewitt of 400 large employers found that one in every eight plans with a company stock fund in their 401(k) made matching contributions in company stock.