I know people that do this. If you are doing it correctly then there is no deception, both companies are aware and expressly allowing it. The key condition is t

I know people that do this. If you are doing it correctly then there is no deception, both companies are aware and expressly allowing it. The key condition is that the two companies are not competitive. Unstated, the people who are allowed to do this are superstars who are incredibly productive even at a reduced capacity. Companies view it in terms of retention risk: 75% of a superstar is much better than forcing the superstar to choose, which may leave you with 0% of a superstar.