The finest gold is that which is genuine and passionate, from the widest range of users and pure (no influence from test conditions). Better still if it was free, ongoing and took little or no effort to obtain then it would leave more time to focus on design.
The rise in popularity of Twitter prior to the launch of T-Hub provided an unprecedented opportunity to observe what real users were thinking about the product.
Previously when you released a product you pushed it out and hoped it was well received. The lucky projects benefited from some user testing but it would be limited in scope, time and the impact of test environment/conditions.
Product release was akin to putting a bottled SOS message into the ocean. From the shore you can anticipate what the journey might involve and prepare the bottle & message appropriately. Then you can wait for the right tide and weather conditions for success, but without ongoing monitoring and adjustment you have no influence on whether it will reach a target.
With a simple Twitter search and something like Tweetdeck you can see the genuine and unsolicited shouts of hundreds of users in real-time. As tweets are naturally skewed towards the very positive or very negative they are naturally the most useful to act upon. These passionate comments provide a general sense of what people find good or bad as well as pinpoint feedback. Our project has used these to change direction and focus, sometimes quite dramatically. The entire resources of the project has been shifted more than once in direct response to such customer feedback. Like putting a punctured inner tube into water, it is easier to fix a problem if you can pinpoint its location and see how big the leak is.