We can't track down 8 million anonymous criminals currently. We *can* track 8 million registered criminals.
Ergo, it makes sense to figure out some sort of incentive plan (e.g. a plea bargain) that convinces illegals to voluntarily register themselves. In the process, lets register their employers while we're at it.
Oddly, we can track all of the illegal aliens who would be eligible for legalization under the President's plan, through the workplace verification program. Those we can't track would remain anonymous anyway.
What will their response be to the Bush plan? What is the President's plan to deal with the millions of illegal aliens who would not be eligible for his guest worker plan.