I'm not a programmer, but I've seen startups co-founded by engineers try hiring designers in a similar fashion to I assume programmers as they test designers with a variety of unpaid projects. I've found it to be pretty annoying given that I've already shown a portfolio of work and it's not unlike spec work. I get that some people may have fabricated their history, but that's why some companies do a trial period before committing to a full-time gig.