Maybe I'm just inexperienced, but can't you get around this with contract-to-hire? E.g., bring your prospective salesguy in for a 90-day contract, and if they cut the condiment of choice, keep them?
Companies that hire Permatemps [2] can get bit hard. As a regular contractor I work hard to keep that line very clear.
[1] http://www.irs.gov/businesses/small/article/0,,id=179115,00....
[2] http://en.wikipedia.org/wiki/Permatemp#Vizcaino_v._Microsoft
And if that became the norm, I'm not sure the ploy would stay legally viable.
Added after reading the fine article: I'd really wonder if it would fly in Illinois. Surely the author has considered it?
However, you might have trouble getting people with families to take the job, especially if they're relocating.
And, yeah, I'd forgotten about relocation, that makes it a non-starter for a lot of people and types of jobs.