1. Genuine candidates: I'm going to quote the extreme, people like Satya Nadella, Sundar Pichai, Vinod Khosla etc. came to the US on H1B and there are a lot of other "superstars" on H1B or naturalized citizens. More practically, there are thousands of other talented people from all countries who work on H1B. So the argument that H1B should be done away with is absurd, unless the US doesn't care about staying atop of the technology sector. Also, H1B workers get paid the same as local workers; there is a minimum wage requirement that has to be satisfied by the company applying for the H1B. So if you buy the allegation that wages are being depressed by H1B workers, why don't you take a peek at the bulletin board of your break room (which have H1B applications with salaries posted) or online and lodge a complaint with the state department of labor rather than posting bigoted comments?
2. Candidates hired by "staffing" companies: Blanket applications made by these "staffing" companies which may or may not have actual jobs. These are the applications that need to be stopped/scrutinized by USCIS (they have tightened this during the recession 2008-2010). It's arguable there is a genuine requirement for staffing companies, but these need to be scrutinized thoroughly.