Raising $11.5M in total commits them to generalising though, and there's no shortage of competent competition in the market-data aggregation space.
At what scale and how long would that take? The VC/angel money allows you to move faster, take more chances and perhaps hire better and faster. And lose money. Important point.
Look at their pricing:
http://mattermark.com/#pricing
Then this:
"Today, Morrill’s curiosity and her 27-person team’s"
Imagine the payroll for those 27 people and how many subscriptions they have to sell with what is (for now) a niche product.
What are the figures on fully loaded labor costs for a 27 person team?
Probably somewhere around $2mn - $4mn/year. That's a pretty big team for the amount of money raised to this point, they must be doing ok subscription-wise.