David Gassko of The Hardball Times has a feature he calls the THT dartboard. They rank all 30 Major League Baseball teams by something they call the "dartboard factor", which is the number of wins a team would be expected to get -- over the 162-game season -- if they played an average schedule and hadn't gotten particularly unlucky or lucky in winning close games.
This seems like the exact opposite of what I would call a "dartboard factor". I would think the "dartboard factor" would be how much of a team's record is due to luck, or to playing an easy or hard schedule. Incidentally, I'd say that strength of schedule is a luck issue, because the schedule makers aren't supposed to take into account which teams are easy and which teams are hard, so it's not nearly important in baseball as it is in a sport like (American) football.
For example, they say the Phillies will go 78-84 this season, and they call 78 the "dartboard factor". The Phillies are currently 37-35; over 162 games that projects to 83-79. (There ought to be some regression to the mean taken into account here, but the mean is a .500 team anyway, so I'll ignore it.) So if I were going to call anything the "dartboard factor", it would be the five "extra" games that the Phillies will win (assuming they keep going at this pace) over the 78 they "should" win. Dartboards are about luck, not skill. I'm reminded of the semi-mythical people who pick stocks by throwing darts, or their modern-day equivalent, the million-dollar waitress.
I won't comment on where their predictions are coming from, because the links in the original post don't actually make it clear.
Also, my guess is that luck doesn't play a big a role in baseball's regular season as it does in, say, football, because there's more time for everything to even out. (Also, football has more season-ending injuries than baseball -- that sort of thing can really screw a team over -- although baseball certainly isn't immune.) Teams get lucky in the playoffs -- anything can happen in a short series.