Again, the data has to exist somewhere for this to work.
On your website you give an example of being able to find pizza lovers from Melbourne. Can you be more specific about how your platform could accomplish this? Saying that contributors will find the data on the internet isn't a good answer. How would someone identify me and track down my info if I should be on that list?
For example, in forums for pizza-lovers. Or in the specific group on facebook. Again on the Facebook - among the people who liked the pages of Pizza-restaurants in Melbourne.
That makes sense, don't you think so?
