Personally, I think that illegals do a great injustice to the immigrants who worked really hard to come here legally.
I also think that in many cases, they are hurting themselves, and the local economies they move into. So many abuses and crimes occur because of and are inflicted on illegal immigrants. People will abuse the crap out of them, pay them next to nothing, work them til they drop, and take criminal advantage of them. They impact local economies because people can 'hire' them for pennies on the dollar (illegally. Many are paid well below minimum wage), and they are often victims of crime because they will usually not report the crime. So, I think illegal immigration is bad for the country, unfair to legal immigrants, and encourages crime of all sorts. It's bad for us, and its bad for them.