The problem isn't really exclusive to steemit. You have any idea how many fake profiles there are on FB and other social media sites created with malicious intentions?

It's an uphill battle with no real solution. Taking people's phone numbers on account creation is a way to combat this, using pictures and video verification for intro posts is a good way to verify... but short of requiring passport verification (which would anger a lot of people), I don't see any way to combat it.

Only thing we can do is pay attention to who we're rewarding on here IMO.