There have been a number of comments in the blogsphere about how Santana's no-trade contract had the Twins over the barrel. It is rumored that Seattle was interested in Santana, but he told the Twins he wouldn't waive his no-trade clause for a Seattle trade. There may have been other teams interested as well, but Santana's no-trade clause gave him the power to limit the market. The result was the Yankees, Mets and Red Sox were really the only teams in the race.
I think this misreads the situation. The Mets were probably not prepared to surrender four top prospects without an agreement from Santana on a long term contract. Likewise, with or without a no trade agreement, any other team giving up that much value would want to make sure they had more than a couple draft choices in compensation after one year.
The reality is that Twins only controlled one more year of Santana. With or without a no-trade clause, Santana had complete control over who he plays for beyond 2008. That, not Santana's no-trade clause, was the real limit on the value the Twins got for Santana.
Some people have suggested the Twins have "learned a lesson" and won't be handing out any more no trade agreements. Hopefully that isn't true. The Twins, like most teams, are reluctant to give players no trade agreements. But the Twins, have also been very successful creating the kind of environment where players want to stay. As a result, some players have been willing to give them a hometown discount. That kind of deal is tough to get without assurance for the player that he won't end up playing cheap somewhere else. It would be foolish for the Twins to abandon all no trade deals because of the experience with Santana.