It is a reward if a.)they don't have to return to their home country to get it and apply like everyone else and b.)they somehow can gain an advantage for already having been here to find a job. Personally, I think that anyone who has ever been here illegally should permanently be denied a Visa as it is obvious that they are willing to break our immigration laws.
Give them a hundred or a thousand dollar fine if it makes you feel any better. My biggest concern is not that someone will get to naughtily jump in line, but that terrorists and criminals will arrive. Anyone who claims that line-jumping is their big reason to oppose President Bush's proposals for immigration reform need to reform their own values and priorities.