David Ortiz was the clear favorite at the designated hitter spot. Hitting .302/.383/.565, Ortiz has nearly twice as many homers as the next closest DH, and has successfully re-established himself as one of the top middle-of-the-order bats in the game.
While Adrian Gonzalez' bat hasn't been quite as dominant as that of Miguel Cabrera, the defensive disparity is pretty huge, which should make up for the small difference in offense. Gonzalez also leads the league in some of the more widely-appealing stats such as RBI and batting average, making him an easy choice for both new and old school fans alike.
Of course, it wouldn't be a Sox-focused All-Star Game post without mention of the completely undeserving Yankees who got the nod. Thankfully, Alex Avila managed to overcome Russell Martin, so we don't have to talk about that. Buzzy has even covered the ridiculousness of Robinson Cano's selection here. But there's nothing more indicative of the fan voting system's flaws than Derek Jeter--also known as Captain Groundout--being given the starting shortstop position. His replacement Eduardo Nunez is actually showing him up offensively.
There's also some question as to what kept Jacoby Ellsbury out of the lineup. The answer is simple: Josh Hamilton's star status. He's got one of the best triple slash lines of all outfielders in baseball, but hasn't been able to play the whole season. Realistically he hasn't really earned the spot, but at the very least he's a good player, and a reasonable selection were it not for the injuries.