Unless, of course, you're looking for a long term contractor and not an employee.
Getting someone to do actual work during an interview is also a no-no. As soon as someone walks through your door and you ask them to do actual work, they're your employee, period. They are now automatically entitled to compensation and a minimum severance period. You can interview people in almost any way you want, but as soon as it involves doing actual work, you're toast. This may be different where you live, but it strikes me as being unethical at the very least.
Hiring is hard. But exploiting people (by expecting them to do actual work, homework, forcing them into temporary contracting) is not the answer.
EDIT: this would be nice on the other hand to get to experience the 'real' culture and work environment at a place before I decide to commit to them.