This is not the case. You can burn through time, money, health, and other consumables chasing bad ideas and, if you're not measuring obsessively, not even know you're doing it until the company suddenly fails on you. (This is even more possible if you're not "in the loop" : many startups with actual employees which flamed out had highly motivated bright people who were hitting their performance targets, in the service of a business which just didn't work. That fact is, ahem, not always clearly communicated to all employees.)

That said: owning the effing company at least means that, if you're getting screwed out of something-to-keep for each hour you work, you should at least know whose fault it was. I really recommend it if working for The Man starts to feel exploitative. (Heads you win, tails you find out why The Man was offering you the terms he was offering.)