Some people boasted about 10,000 people using Steemit but, judging by the pending payouts, almost all the activity is $0 / "freemium users".  Getting a force of 10,000 out is sizeable in the crypto but it makes it nowhere as popular as Bitcointalk dotorg and isn't indicative of viral adoption. 

As I've said before - Reddit clones have been tried a dozen times before and none end up viral.

Steemit already has had hacks and the upvoting seems to be a circle jerk over Bitshares and Cleavage.