There are some people (the most notorious being Bill Stoneman, followed by Stephen C. Smith or "FutureAngels") who follow the Angels' minor leagues really closely and become so attached to their prospects that they overvalue them. Case in point: the Miguel Cabrera trade in 2007 that never was.
During the past 10 or so seasons, we've seen so many incredibly-hyped Angel prospects who fizzled out in the majors. It's alright to have a handful of untouchables (Trout being one of them, as he is a once in a generation player), but for most GM's the general principle is if you are deciding between a proven major league player and someone who has never played in the MLB, you go for the proven player.