The management pushing the stock and painting a rosy picture while behind the scenes the ship was sinking.

The employees putting everything they had (and then some) into a single stock from their employer.

I don't know if there was criminal behavior involved but an imbalance of information was in play that cost the employees everything and then some.

The tragedy of Enron was the automatic investment plans in the 401k for most employees. The default choice was Enron stock. Also, depending on the nature of the matching contribution, Enron stock might have benefited from a larger matching employer contribution percentage or discounted share price. This is why 401k plans now offer various choices that are suitable and diversified for most people.

http://blogs.wsj.com/moneybeat/2014/07/04/are-you-stuck-on-y...

A defined benefit plan could have prevented this tragedy. It's funny though. Defined benefit plans are mocked at by large firms but increasingly being used by wealthy individuals/families and their small businesses. Nothing beats government subsidized PBGC insurance for the future retirement plans of America's job creators.

Various accounts of the Enron saga include anecdotes of employees happily (and being encouraged to) invest most or all of their 401k in Enron stock.

I believe before the collapse Enron's management would berate employees who sold stock in their 401-ks. Management actively mislead their own employees. I've heard this from a number of sources (including a family friend who left Enron a couple years before the collapse.) Obviously, take my comment with a grain of salt since it's mostly based on anecdote.