But they might not want to break the law in the future

That is the reason George Bush gave for granting telecom immunity at a press conference this morning.

You can't expect the phone companies to participate if they feel that they are going to be sued... How can you listen to the enemy if the phone companies aren't going to participate with you?

This article from the Economist responds to this claim...

How are you going to listen? Well, presumably by way of lawful court orders or emergency certifications, as authorised under the old FISA statute, and now also on the independent authority of the attorney-general and director of national intelligence even without a court order, assuming some version of those expanded powers eventually passes. When surveillance is conducted pursuant to the law, there is no question of whether telecom firms will "cooperate" or "participate", like children at day camp. They will comply, and they will do it because they are required to.

The worry about "participation" makes sense only if you anticipate asking these companies to turn over information outside the law, without a court order or any statutory authority. But that is precisely why we have laws establishing penalties for unauthorised data disclosure: To deter them from helping the government to circumvent the law. If you think they should help the government circumvent the law, then it seems you ought to stop poncing about with ad hoc amnesties and simply do away with the data disclosure statues, at least as they apply to information sharing with intelligence agencies.