There's a trend among start-ups (and some larger companies) that worries me: giving candidates "homework" assignments. Homework assignments lead to candidate abuse. Knock it off (or at least be reasonable). I've seen many friends and clients go through this. As a pre-screening round before an onsite interview, a company gives them a "homework" assignment. This takes them hours to complete, but they finally submit it. A few days later they get the canned "thanks but no thanks" email. Not cool.

From a company's perspective, I get it. Homework assignments offer a company an ability to see how a candidate completes a relevant project, and one that's a larger scale project than what can be done in a timed interview. And, hey, it's basically "free" for the company. Someone has to review the project to give a thumbs up/down, but that doesn't take too long.

And that's the problem: it's free. Interviews have a nice limiting function; if it's a waste of the candidate's time, then it's a waste of the company's time. Not so with homework assignments. Homework assignments remove the disincentive for a company to not waste candidate time if there's even a slim chance of the candidate working out.

This is exactly what's happening. Candidates spend many hours completing homework assignments for companies which are not sufficiently interested in them. This is abusing candidates. Knock it off.

If you are going to give homework assignments, make sure you set up a procedure that prevents (or limits) such abuse:

Understand whether this is a "screening" round or an "evaluative" round. If it's an evaluative round, then this should be truly part of the decision-making process for an offer, weighted equally with actual interviews. In this case, you shouldn't need so much time in the interview itself; this was part of your interview. (But are you sure it should be evaluative? How much help did the candidate get from friends?) If it's a screening round (where the homework isn't used much beyond a yes/no decision to proceed), then the homework assignment should be fairly short. It's not nice to make candidate spend a lot of time on something that you're only going to use to give them a thumbs up or down.
Keep it short.The longer the project, the more it is abusive.
Keep it timed. If you time the homework, it prevents candidates from spending enormous time on it. It also makes the time investment explicit to you.
Screen well beforehand. A homework assignment should never be the first step in a screening process. Homework should only be given when a good fit has already been established.
Have a high "pass" rate. If 90+% of candidates aren't progressing past the homework, you might have an abuse problem. In an abuse problem, companies are giving homework to candidates who are unlikely to make it. Figure out why you're giving too many poor fits homework, or figure out why good fits aren't doing well.
Make your expectations clear. To prevent the "if I want this job I must write up a 50 page report" issue, make it clear to candidates what it is expect. How many slides? Do they need to worry about the design? How long should each write up be? The clearer your expectations are the less likely to are waste a candidate's time.
Deduct it from onsite interview time. A typical company might send a candidate in for a full day (6 hours or so) of interviews. If you're giving an additional six hours of homework, that's not okay. Every hour of homework should remove at least 30 minutes of onsite interview time.
Monitor the system. Ask candidates (after a decision has been made) how long they spent on the project. Your homework assignment might be taking them a lot longer than you expect. Realize though that candidates will probably understate the work in an attempt to look smarter.

Remember that candidates have other things to do with their lives. They have families to be with, activities to do, jobs to work, and other interviews to complete. They don't have the time for this. If you unfairly require homework, they will be turned off by your company, potentially quit the application process early, and tell their friends. So knock it off, okay?