The sign up incentive is a great reward and program from the devs to be sure. I think it's the one thing that causes people to stick around, incentive wise, if we forget about the actual network for a second.
That being said, there's multiple ways of interpreting value to posts; entertainment, network, social, emotional and monetary value all play a role in the overall picture that is steemit. I think this post and the ones before it fill a niche. An attractive and 'hot' social and emotional niche that might get people chasing for that 'big dollar amount they saw tara make'. This will lead to more signups and to more 'money and time' entering the system.
I am however, skeptical of the longterm value of it all. What will the new sign ups who came for tara's success do when they make only 1 cent? Will they stay for the network? Will they leave because their goals seem impossible to reach?
Moreover, what will we do with all the obvious copycat schemes and rehashes of content that was deemed 'valuable' once? The 'fad status' may not be beneficial in the long term. When people don't reach their goals, that might actually become a negative force of entropy to the steemit ecosystem, discouraging their friends and contacts from even trying 'because they barely made a cent and got lost in a cacaphony of rehash and get-rich-quick'.
Powering down takes two years. Will posts like these still be relevant and valuable in two years? Maybe. Maybe not. Time will tell.
I've elaborated on my views toward Steem marketing and social capital here: https://steemit.com/value/@spookypooky/posts-on-steemit-aren-t-valuable
If they stick with it they will be helped by other users, who in turn have helped us. If someone wants to immediately jump in and start posting, they can try, but it most likely will not work. I'd rather have people who want to learn and create better content stick around than those who just want to make a quick buck. And once we a whales when we help new users it helps them out and at the same time helps us out. I don't really know where steemit will be a moth from now or even a week, but I love the thoughtful creative and uplifting community. Those who are actually being themselves and not trying to be something they are not.