In 2007, over the course of about 3 months, The Wife and I had a an animated series of discussions about our very active stock portfolios (at the time we were not married, maintained separate portfolios, but knew one another's portfolios inside and out). The concencus we reached was shocking, we had no business investing in stocks. The key reason was simple, we were not privy to the information that insiders were privy to. Without access to the books, and managers, we could not make effective decisions as to whether a company was a good investment or not. Based on this, we concluded that stock investments were not suitable for the average individual, but only for the very wealthy. In the end, both The Wife and I, liquidated our stock portfolios around the middle of 2007 (I placed the sell order a couple of days ahead of the crash, unfortunately, my budget trading account took up to a month to clear).
This article indicates that not only was I right, but that modern corporations are too complex for even the insiders. If a CEO does not have sufficient information to be investing in the company he is head of, neither do I.