This makes me wonder a bit. If San Diego had been interested in JD Martinez, it would have allowed Boras to potentially demand more from the Red Sox. But let's look at it another way. Boston was always going to be the top bidder for JDM, or at the very least, close to it. But what if the Padres turned around and offered JDM 5/130, and he signed there, after the Red Sox had already signed Moreland. Suddenly it's Hosmer on the outside looking in.
By managing two clients who are potentially competing for spots on some of the same teams, perhaps Boras has to decide which client to "screw over", in order to best line his own pockets.
I mean, if he had to choose between Hosmer getting 8/140, with JDM getting 5/115, versus JDM getting 5/130 and Hosmer getting 4/64 - what's Boras going to do? Maybe it wasn't so much of an issue before, with bidding wars and such, but there seems to be a very limited market for these types of players right now. In this case, it doesn't seem to be very egregious, but I could see a scenario where there may be potential ethical violations and lawsuits.