Political research organizations.
If I'm reading this right, it's 500 tweets per request, or 5,000,000 tweets returned for 10,000 requests per month.
Which seems at least the rate that most political pollsters and research organizations would be eating to figure out what's happening with opinions in hot races.
Got a city the size of New York or Paris and want to track people's opinions for tight race? Twitter's got a big dataset that's all juicy and waiting for you. And up to now it seems that companies have been used to getting that each night to grind for the morning's reports.
But, that also is hitting medical and social research right in the nuts. Lots of universities have got pre- and post-grad students gleaning info from twitter just to keep track of how their own University campaigns, student or staff initiatives, and outreach are doing. They're going from zero dollars a month to $149 per research project, basically.
Unless they want to "enterprize-size" it.