Poor Dan is the businessman who didn't quite make it. He ran everyone's favorite Old West sounding railroad, the Phoenix-Durango, which mainly provided service in Colorado. But Dan was the unfortunate victim of one of the looters' early laws, an absurd regulation that prevented him from conducting business in Colorado. Dan doesn't get angry and quit and set his trains on fire (a la Ellis Wyatt). Instead, he becomes confused and sad. He's beaten down and he accepts his defeat. It's never clear if Galt ever tried to get to him; perhaps Galt didn't feel his morals were properly squared away.
[Dan:] "Dagny, the whole world's in a terrible state right now. I don't know what's wrong with it, but something's very wrong. Men have to get together and find a way out. But who's to decide which way to take, unless it's the majority? I guess that's the only fair method of deciding, I don't see any other. I suppose somebody's got to be sacrificed. If it turned out to be me, I have no right to complain." (18.104.22.168)
Dan provides us with yet another picture of what happens to decent people in a world run by, and largely defined by, people like the looters. He has taken in their rhetoric about "sacrifice" and the "majority" even if he doesn't fully believe it. He just can't see any other way of doing things.
Dan can't resolve the contradiction between what he feels is right and what he's been taught. However, we do get a sign that he gets some of his mojo back, when we learn that he refused to sell James Taggart his railroad in Colorado. That sends James into a tizzy, although sneezing probably prompts hysterics from him, so there you go. The point is that while Dan may not have been an active member of the strike, he did share many of its views and values, and he set out to live independently, if quietly and sadly, from the looters.