If a founder works on his company for a year, but can't seem to make it work, do future hiring managers see that time spent as a negative (couldn't find a way to make the company work, why would we hire them) or a positive (imagine all the lessons and skills they have developed in that year)?
Would that year in the startup put you ahead of the pack, or behind it, since you would essentially have one less year of traditional work experience.
Let's think of the red flags there: 1) Doesn't have a clear conception of what he's capable of. 2) Unwilling to get hands dirty and code. 3) Because of this, didn't learn any technical skills that'll be useful in the job. 4) Won't take responsibility for his own failures.
In almost any other situation I can think of, doing your own startup would put you way ahead of the pack. I was actually pretty excited about the above candidate when I saw "founder" on his resume, 'till he blew it in the interview.