These guys committed the cardinal sin of emailing me over an assignment to complete in my spare time (after a fairly stilted but generally fine phone interview), which involved building a UI from a slightly confusing spec, but then after I completed it over a couple of evenings and sent it over to them, I never heard back. They told me I was applying right at the end of their hiring period and they'd seen some good candidates already, which I should have taken as a big warning sign, but still they could at least have politely responded to my email. The assignment took probably 3-4 hours to complete if done with carefully structured and well-commented code, which was in hindsight a complete waste of time. It wasn't even a fun challenge. There is no excuse for asking people to give up a chunk of their free time at such an early stage of the interview process and then not responding to them.