Ohio U. poli-sci professor Patricia Weitsman argues that the U.S. ought not to rely so heavily on the concept of coalition warfare:

Relying on one’s partners to fight wars makes sense. After all, it is better to fight with your friends at your side than alone, right?

Wrong.

When waged for the wrong reasons, coalition warfare is more costly and less effective than fighting alone. Coalition warfare requires a high degree of joint planning, consultation and cooperation. The presumption is that this loss of autonomy is more than compensated by having coalition partners provide additional troops on the ground and share the burden of fighting.

Weitsman goes on to point out that [with the possible exception of Great Britain] the American-led coalition in Iraq has been much more useful as a public relations tool than a military one. I can't help but agree. If another country wants to help the U.S. by making a legitimate, valuable contribution, then by all means, let them. And a troop is a troop is a troop. But when bare-knuckle bribery comes into play... is it really worth the hassle?