If the work is in any way usable to the interviewing company, definitely. We went that route for one of our work samples where abstracting out a context-mirroring scenario was going to be very difficult. We then paid the candidates for the time spent doing the 4-hour take-home work sample.
One anti-pattern here involves turning all of your work samples into week-long consulting engagements. Those are a great way to evaluate candidates, but it means you can only hire folks who are already doing consulting (or are otherwise unemployed). For some companies, that works.
