What's wrong with Immigration?

Is immigration really that bad? Why? I'd rather give immigrants here a job if they will then spend the money here... it would help the economy more than companies sending the factory down to mexico.  At least if they live here, and buy things here, it will help the economy here, rather than the alternate... as I said.. our companies go searching elsewhere for cheaper labor.  What do you all think?

>>1
I agree, I think it is better they have their jobs here in the USA, and reinvest the money here in our economy than taking it back to theirs after being deported due to some 'guest worker program' or some such bs.