Lord Bling had an excellent post below, which resulted in some even more excellent responses in comments. Read them, and then come back to this post.
Cowboy Law and Hispanic Causing Panic (HCP) have had some thoughts along these lines in previous posts as well, so I should also acknowledge their roles in shaping this post as well.
The idea of border control, even with a gigantic fence is laughable. Do you think any fence could stop this kind of thing from occurring? Only if it extends down to the 10th ring of Hell. I'm not sure how much that kind of excavation would cost, let along what government contrators would charge for it. Conservatives, in particular, get a feeling of safety from having a giant wall along our border with Mexico, despite lots of evidence to suggest that a wall provides very little in terms of deterrance. That didn't keep the Republicans in Congress from passing a law to do this recently. Our borders are pourous, and will continue to be. Deal with it.
If we wanted to end illegal immigration tomorrow, the only thing we would have to do is enforce the existing laws and levy enormous fines upon businesses and individuals who hire illegal immigrants. Demand for immigrant labor would cease, as the economic incentives (cheap labor) would disappear. Produce would become a delicacy. The fines would more than pay for the cost of increased enforcement. If people wanted to work and employers wanted to hire workers, they would be forced to do so legally. The economic impacts of doing this could be significant, but at least we wouldn't have all these criminals washing our dishes, landscaping our yards, and picking our strawberries.
A friend of mine owns a landscaping business in Omaha, and has made a decision not to use illegal labor, despite the fact that doing so, negatively impacts his ability to bid competitively with other landscaping businesses. He does this because he feels that hiring workers for $2/hour is expoitation, not because he is afraid of getting caught. The fact that we likely have over 10 million illegal workers in the US, shows how dedicated the government is to enforcing current laws.
The bottom line is make all the laws you want. Demonize illegal immigrants as criminals, while ignoring their contributions to making our economy tick. Hell, while you're at it, give President Bush credit for making the economy better, despite the fact that he has had NO direct impact on the economy. Name one policy or piece of legislation that he has been a part of that has improved the economy. I'll go find Bigfoot, Santa Claus and a cure for cancer while you do that.