Not necessarily, in some MLS areas we are able to distribute on behalf of the MLS vendor. It's on a case by case basis and still requires us to ensure we are working with a valid broker, though.
> It's not like building an app on the Twitter or Tumblr API, you have to call the MLS office and talk to real people (who are usually experts in real estate, not tech) and often pay them real money.
In general, this is true. However, we are simplifying the process :). Usually, we are able to handle all the dirty work with the MLS vendor on behalf of the broker. Especially in areas where we have a licensing agreement with that MLS already. Not all MLS's support this but we are growing our reach to handle this as smoothly as possible.
> Also, I'm guessing your IDX feeds don't always include sold properties or historical data.
We can only support what the MLS vendor supports but gaining access to sold and historical has only a problem in smaller MLS areas. It usually costs more at the MLS level, though.