Guillen, Ordonez, Meche are players you can get for a reduced return in talent. If they turn out to fill a position of need (say Drew gets hurt, we might go for Ordonez, or if we lose Lowell Guillen would be tempting) then it can be smart to pay the money and sacrifice little talent to add a veteran whose contribution to their present club is overshadowed by a contract we can afford to pay.
Young, Bedard, VMart are players who the only way they're available at all is their contracts, and those are opportunities to be pursued as well.
Hey, if Lowell gets hurt, Smoltzie's doing well, and Atlanta's out of it at the deadline, who knows, we might even see Chipper in a Boston uni