Manny Ramirez has been placed on waivers by the Dodgers, and it looks like the only teams that want to claim him are AL squads, particularly the Rays, Rangers, and White Sox. This is likely because of Manny's declining defense, and is totally understandable. But the Giants shouldn't pass up this opportunity to help them now and in the future by claiming Ramirez on waivers. If they do so, essentially two situations are possible:
1. They get him. Ramirez is still a damned good hitter, even if he can't play the outfield anymore. We're already overcrowded, but acquiring Ramirez would make Guillen totally unnecessary and hopefully result in a DFA. However, we shouldn't pursue this option too vigorously, offering only a mediocre prospect or nothing in return for Ramirez, both because we'd probably end up paying his salary and because we don't really need him.
2. They don't get him. As weird as this sounds, this is actually the preferable (and more likely) option. The Giants don't need Ramirez, they probably would have problems paying his salary, and the Dodgers likely want real prospects in return. Plus, they aren't likely to trade him within the division, and I doubt the Giants offer him the extension he wants to waive his NTC. But considering his only suitors are in the AL, it's unlikely that blocking a Ramirez trade would result in a diminishing of the Giants' playoff chances; in fact, keeping him in LA would probably hurt their odds, and only help if they made the World Series.
However, I think there's an argument to be made for blocking a Ramirez trade not to another team, but out of Los Angeles. Ramirez is the best available upgrade, and would be a significant asset to an AL team that could DH him. It therefore stands to reason that the buying team would part with a legitimate prospect or two to acquire him; in other words, a player that could make the Dodgers better in the future. Given that the Giants have to contend with the Dodgers for a playoff spot probably forever, forcing LA to hold on to a player that won't help them now or in the future instead of allowing them to acquire a player (or players) that may help them in the future seems like a pretty good move. And the absolute worst case scenarios aren't that bad; if the Dodgers just let Ramirez go, the Giants have an overqualified, overpaid pinch-hitter, and if he isn't worth any prospects and goes to an AL team for nothing, the Giants would prevent LA from obtaining salary relief.
IMO, the reward outweighs the risk here pretty considerably. It'd be nice to see the Giants make a solid chess move like this, considering it would be done with more than just this season in mind, and show an appreciation for the value of minor league players. Of course, that means they won't.