In publishing anything we are subject to copyright compliance, though the playing field for the free designer pool is a bit "anything goes". For the premium designers, watch face designs pass through a formal QA audit (that includes brand/copyright checks) before being published in the Facer store.
Personally, even though I may replicate or "be influenced by" (pay tribute to... ,etc), I always try to make my designs my own in some way.
Yes, knock-offs are always a huge business - look at Orris watches which closely resemble Rolex. Even Tudor watches are very close knock-offs - and they're owned by Rolex lol.