I'd say there is one big difference between Steemit and Facebook. On Facebook when I get a like on my pic it is very different than on Steemit because on Facebook these are all people that I know whereas on Steemit I have no real personal connection with any of the people liking my posts. So if for example on Facebook a girl that I like likes my post that much more gratifying than a random person on Steemit liking my post. Facebook has also become a symbol of your social status (which I do not think is a good thing). Whether we admit it or not we judge other people based on howmany likes they got on their posts and pictures. Its a measure of your popularity.
Will Steemit produce the same negative aspects of Facebook? I don't think it will serve as a confidence booster/killer like Facebook does. But Its hard to tell what will happen once we go mainstream and the user-base really starts to explode. Right now my favourite part of Steemit is the community/people on here. There are no trolls yet, and people are genuinely trying to contribute real, useful content. And the big difference here is that on Steemit people are trying to make A) learn from high-caliber people B) earn a little extra money, not gain some sense of self-worth like they are on Facebook.
Jeez that was a longer post than I was planning to write:P