What kinds of outreach did you do during the early days?

Savkar's first response bears witness to the importance of cultivating advocacy among early adopters, especially those who are established as authorities in the field.

"For the first few months, we were focused entirely on leveraging degrees of separation," he said. "There was a group of around 20 to 30 scientists who had worked closely with us to design the offering, and they were our initial advocates to their colleagues and connections, who in turn reached out to theirs. You might say we used something like a closed beta approach to building the initial community, even though the site itself wasn't actually closed to outsiders during that period."

In your experience, what factors contributed to a large group of users registering?

A diverse and pervasive promotional strategy narrowly targeting the niche market was key to Scitable's early growth, Savkar told us. Initial activities included industry-focused advertising, a few influential bloggers' posts, a "modest but active" Twitter following, and good SEO.

"Although it's difficult to pin this down exactly," he said, "I think that it was the convergence of all of these media - hitting the same people multiple times from different angles over the same period - that helped push people over the action threshold."

What about Scitable do you think made people want to sign up and start using the site?

Scitable's success as a scientific resource has been all about credible and accessible information. Their parent company, Nature Publishing Group, has a strong reputation as a publisher of science research, a fact that Savkar said was important to early users.

Another important factor was that Scitable was designed to solve an industry problem, to meet a tangible need for "credible, accessible online reference and educational materials in the sciences," Savkar said.

"I think the basic message of what Scitable is aiming to do resonated with people right from the start. And once people were driven to the site... users were able to find their way to useful and high quality material quickly. That, ultimately, is as much of a draw in educational sites as it is in e-commerce."

What did you learn about handling large amounts of traffic? In your case, were there unexpected spikes?

"We had the advantage of being part of Nature Publishing Group," said Savkar, "so right from the beginning we were in a robust data center that had a sizeable hardware runway built into it and had the benefit of a great sysadmin team that has been through a number of launches."

And although he said scaling was a relatively smooth process compared to the experiences of some startups, Savkar said that Scitable also had its share of glitches, blips, and downtime.

"Some high-traffic blogs covered us without our realizing it, and that drove big peaks over a period of a few minutes when the stories first ran. But we were aggressive with our load testing before launch, so the spikes were within our cushion and the site performed fine."

And when the site wasn't running as well, Savkar said, "What we learned was how important it is to have an easy way to provide messaging to our users when things are operating at less than 100% performance," he said. "Users in general will be patient if you're forthright with them about what's happening."

What are your future plans for scaling?

In addition to expanding the content subject material (current topics cover genetics only), Scitable has also seen a lot of interest from high schools and is accordingly broadening the intended age range of users to include high school students. International expansion will also become a greater focus for the site, "not only because the numbers are so large," said Savkar, "but also because in many places overseas the immediacy of service we're providing is a stark improvement over the current situation.

"We're exploring both partnerships and direct outreach approaches to reach those markets, but search results are always the fastest way to go international."

If you could pass on one piece of advice to the founders of the Next Big Niche Site/App on how to get a critical mass of users, what would you tell them?

Users don't want to network for networking's sake. Time and attention are at a premium. Sites need to provide value, then "facilitate network effects" around that, Savkar told us.

"Outside of the small handful of truly big social networking players like Facebook and so on, social networks need to provide something more than just networking to draw and retain users. For us, that something was premium content, which... becomes a kind of watering hole around which people can gather and then have ad hoc interactions with each other that can turn into long-term interactions," Savkar said.

Ultimately, a deep background in an understanding of their industry has helped Scitable to develop content around a specific need, target a highly qualified audience, and discover new opportunities for expansion.

Are there other important factors for niche-focused startups to consider? If you're an entrepreneur or VC with similar experience, what have you learned about working successfully within narrow verticals? We'd love to hear your stories - please email us or share your wisdom in the comments below.