What's wrong with having "guest" workers?

My objections to the “guest worker” provision in the proposed immigration bill are two:
(1) we already have a guest worker program on the books, which employers apparently find too troublesome to use; and (2) it is not just the dishwasher ranks whose wages will be depressed, but also our professional ranks, from IT people and engineers to nurses and physicians.

The current American way seems to be to pay as little as an employer can get away with, and it can get away with a lot when there is a pool of people for whom even our pitiful minimum wage is more than they make where they come from.