I don't think Steemit will be the death of Facebook anymore than Reddit, G+, Twitter, etc ... killed any other platform.

I do feel that Steemit is a wonderful opportunity to engage in meaningful conversations about interesting topics while generating revenue for bringing quality posts to the forefront.

As for ads, they have a time and place. I actually don't mind the infrequent well placed ad about something that interests me. Even though it was paid for, it gives me an avenue to explore something I might otherwise not have.